Methodology: where our numbers come from
Every number on this site traces to a published source, listed below by calculator. Where sources disagree, we show both figures. Where we could not verify a number, we leave it out.
Mulch calculator
Cubic yards = (square feet × depth in inches) ÷ 324, a constant Clemson Cooperative Extension states directly: one cubic yard covers 324 square feet at 1 inch deep.
Depth varies by mulch type and extension office. Shredded bark runs 3 to 4 inches on well-drained sites per Iowa State University Extension, dropping to 2 to 3 inches on heavy soils. Gravel used as mulch gets 1 inch from Clemson and University of Maryland Extension, shallower than some landscaping blogs suggest; we use the extension figure. Bag sizes come from retailer pages: 2 cubic feet (Vigoro) and 1.5 cubic feet (Earthgro) are the two dominant sizes; bags per yard is 27 divided by bag size.
Topsoil calculator
Same formula as mulch. New lawn establishment calls for 4 to 6 inches per Penn State Extension. Raised beds get a wider range: 4 to 8 inches for a finished bed per Clemson, up to 12 to 24 inches for deep-rooted crops like tomatoes per University of Maryland Extension. We show tiers, not one number, since extension offices don't agree.
Gap: no extension source gave a weight-per-cubic-yard figure for topsoil. Two suppliers estimate it by moisture level instead: Topsoil.com puts it at roughly 1,500 to 3,000 lbs per cubic yard, dry to saturated. Ottr Landscape Supply puts it at roughly 2,000 to 2,700 lbs. Both figures are labeled supplier-sourced, not extension-sourced.
Board foot calculator
Board feet = thickness (in) × width (in) × length (ft) ÷ 12, per Woodworkers Source. The catch: this math uses nominal (rough-sawn) thickness, not actual planed thickness. The nominal-to-actual size table (a 2x4 measures 1.5 by 3.5 inches actual) is cross-verified against ProWood and Archtoolbox, which agree on every dimension. Two decking sizes, 5/4x6 and 6/4x6, come from ProWood alone and are flagged single-source.
Deck board calculator
Board count starts from actual width, not nominal. Nominal 6-inch decking runs 5.25 to 5.5 inches actual; we use 5.5, the figure both Decks.com and ProWood support.
Gap spacing is where manufacturers disagree, so the calculator asks which brand you're using instead of hard-coding one number. Trex recommends 3/16 inch side-to-side, widening to 3/8 inch in wooded areas. TimberTech splits by line: AZEK calls for 1/8 to 1/4 inch with no end-to-end gap, while PRO and EDGE call for 1/8 to 7/32 inch. The ranges overlap but aren't the same, so we present both rather than averaging them.
Waste factor runs 10 to 15% extra for straight runs, up to 30% for diagonal patterns, per TimberTech. Joist spacing (16 inches on center standard, 12 for angled decking) traces to Decks.com's framing guide and 2021 IRC Section R507.6. Framing is a code matter: confirm with your permit office before you build.
Fence calculator
Post spacing: 6 to 8 feet is the standard range, with 8 feet the common default because it matches pre-built fence panels, per Barrier Boss. Use 6-foot spacing for heavy panels, high-wind sites, or sandy soil.
Post hole depth is where sources conflict, so we show the range. Quikrete: 1/3 to 1/2 of above-ground post height, plus 6 inches. Sakrete: roughly 1/3 of above-ground height, though its own worked example (an 8-foot fence needs 36 inches) doesn't match that rule, which would call for 32; we report that as published. Penn State Extension gives a flat 36-inch line-post depth and 48 inches for corner and gate posts, with no fractional rule at all. All sources agree the hole should clear the frost line by 6 inches, whichever depth is greater. Confirm with your permit office before setting posts, and call 811 before you dig.
A 50 lb bag of Quikrete Fast-Setting Concrete Mix yields about 0.375 cubic feet; Quikrete sets a 4-inch post in a 10-inch, 2-foot-deep hole with 2 bags, matching Sakrete's 2-bag estimate for a 6-foot post.
Gap: the tool calculates posts, pickets, and concrete, but not rails. No manufacturer or extension source publishes a rails-per-section table, so we left rails out rather than invent a rule.
Deck stain calculator
Coverage rates come from manufacturer spec sheets and vary by product, wood condition, and coat number, so the calculator asks for all three instead of using one flat rate.
Cabot's oil-series solid decking stain runs 400 to 500 sq ft/gal smooth, dropping to 250 to 350 sq ft/gal rough. Behr's premium solid color stain covers 200 to 400 sq ft/gal on coat one and 400 to 800 on coat two (direct fetch returned a 403, so this is search-indexed, not a live read). Olympic Maximum Solid states 250 to 350 sq ft/gal, while independent field reviews report closer to 150 to 250 on an aged deck; we use the manufacturer figure and note the gap.
All three agree on the same pattern even though numbers differ: rough wood cuts coverage roughly in half versus smooth, and second coats cover 1.5 to 2 times more area than first coats.
Gravel calculator
Cubic yards = (length ft × width ft × depth ft) ÷ 27, the same volumetric identity behind the mulch and topsoil formulas above, applied to gravel. It's pure geometry, not material-specific, so no gravel-specific source restates it.
Depth by use has no cooperative extension source. Unlike mulch and topsoil, we found no land-grant extension office publishing a numeric depth recommendation for driveways or paths; the closest .edu material covers gravel-road engineering, not homeowner projects. The figures we use instead are supplier-sourced and labeled that way in the calculator: Braen Supply calls for a 4-inch base (two 2-inch compacted lifts of 3/4-inch quarry process or recycled concrete aggregate) topped with 1 inch of concrete sand for patios and walkways, and Braen Supply's pea gravel guide calls for a 2-inch pea gravel wearing layer over a 1-inch base, 3 inches total.
Density is where two suppliers conflict, so we exclude one entirely. Gravelshop.com lists an identical 2,410 lb per cubic yard for every product we checked, including pea gravel, crushed stone, and river rock; materials that different shouldn't weigh the same, so we read that as a flat, generic placeholder and leave it out. We use Stone Center's per-material ranges instead: washed gravel and pea gravel at 2,800 to 3,200 lb/yd³, river rock at 2,800 to 3,500 lb/yd³. Stone Center's own crushed-stone row (5,400 to 6,800 lb/yd³) is roughly double every other row on its own page, so we exclude that row too and use a broader aggregated industry range of 2,700 to 3,400 lb/yd³ for crushed stone.
Compaction factor: loose cubic yards needed = compacted cubic yards ÷ 0.85 × 1.10, meaning you order roughly 15 to 30% more loose material than the compacted volume you need in place. This comes from a single source, ToolGrit, an aggregate-equipment guide site rather than a manufacturer or extension office, so we flag it as lower-confidence.
Paver calculator
Base prep depth is where two manufacturers land in the same range with different framing. Belgard calls for 4 to 6 inches of crushed gravel base for walkways and patios (8 to 12 inches for driveways), compacted in lifts no greater than 4 to 6 inches, topped with 1 inch of bedding sand. Braen Supply specifies 4 inches of base as two 2-inch compacted lifts plus 1 inch of concrete sand for the same light-duty category. The two agree closely enough that we use both, crediting Belgard's range as the primary figure since it's a paver-specific install guide.
Jointing sand coverage depends on joint width, so the calculator asks for it instead of assuming one number. A 50 lb bag covers 75 to 100 sq ft at a 1/8-inch joint width, dropping to 35 to 50 sq ft at 1/4 to 3/8 inch, per Sublime Pavers. Manufacturers generally don't recommend polymeric sand in joints narrower than 1/8 inch.
Waste factor: Unilock's installation spec calls for a minimum 5% overage. Broader industry practice pushes that to roughly 10% for a standard rectangular running-bond layout, though no manufacturer source breaks out waste by pattern (herringbone, diagonal, and so on), so we don't publish pattern-specific percentages.
Paver dimensions come from the Pavestone Holland Stone cut sheet, a manufacturer PDF: 3-7/8 by 7-13/16 inches at 60 mm or 80 mm thick, with 480 pieces covering 103 sq ft per pallet at 60 mm.
Retaining wall calculator
Blocks per square foot = 144 ÷ (face length in inches × face height in inches), basic geometry applied to manufacturer-published dimensions. Two Pavestone cut sheets confirm the formula against their own pallet coverage: the #811 block (11.63 by 4 inches) works out to 3.10 blocks per sq ft, and the ProMuro block (18 by 6 inches) works out to 1.33 blocks per sq ft. Both match the pallet-coverage figures on the same sheets, confirming the dimension readings.
Base trench depth comes from Unilock: 12 to 16 inches deep depending on block height, with 4 to 8 inches of gravel in the trench and at least one full course of block buried below grade. This is a supplier install guide, not an engineer's stamp, so treat it as a starting point.
Engineer thresholds are where sources genuinely disagree on the number, so we show more than one rather than picking a favorite. Unilock sets the practical trigger: walls over 4 feet need geogrid reinforcement, and adhesive-only assembly (no mechanical interlock) tops out at 2 feet. Allan Block's gravity-wall chart gives a soil-dependent ceiling instead, from about 3 feet 3 inches on clay up to nearly 6 feet on sand and gravel, under level conditions with no slope or surcharge above the wall, and explicitly excludes seismic loading. Both manufacturers agree a slope or heavy load above the wall lowers the safe height regardless of the raw number, and both say a registered engineer should sign off on any final design. Structural work: confirm with your permit office before you build, and call 811 before you dig.
Project ROI checker
Data sources: percent-cost-recovered figures come from 2 NAR reports. The 2025 Remodeling Impact Report, published April 2025 by NAR Research with the National Association of the Remodeling Industry, covers interior projects. The 2023 Remodeling Impact Report: Outdoor Features, published March 2023 by NAR with the National Association of Landscape Professionals, covers outdoor projects and is the most recent edition of that report; no 2024 or 2025 outdoor-features update has been published.
We do not use Zonda's Cost vs. Value Report in this tool, even though it's the best-known source for remodeling ROI and the one most sites quote. Its 2025 licensing terms rule out this exact use: "The Cost vs. Value Report, whether in whole or part, may not be incorporated for use in any kind of computer- or Web-based application, calculator, database, or other automated, electronic, or digital device, instrument, or software except as licensed by Zonda Media." A calculator is a calculator, so we left Zonda's figures out rather than borrow them without permission.
Method: for each project, the calculator applies the national percent-recouped figure from the matching NAR report to the cost you enter. Type in your contractor's quote, and the tool multiplies it by that project's recoup percentage to estimate what you'd get back at resale. There's no dollar-cost default to fall back on, since NAR's public interior report publishes recoup percentages and Joy Scores but not the dollar figures behind them.
Caveats: these are survey estimates, not appraisals. The 2023 outdoor report's cost figures come from a survey of NALP landscape-professional members (160 responses out of 1,670 contacted), and its resale-value figures come from a separate survey of REALTORS (1,891 responses out of 42,164 contacted); both surveys draw on professional judgment, not sale records. Both NAR reports carry the same caveat in their own text: local market conditions, supply and demand, and inventory levels can move a given house well away from the national figure. Every result in the calculator is labeled with its report name and year, since the interior and outdoor datasets don't refresh on the same schedule; the outdoor figures you'll see are from 2023.
Refresh promise: we'll update these figures when NAR publishes a new edition of either report, and we'll add Zonda's data if a license comes through.
French drain calculator
Trench size comes from Louisiana State University AgCenter's French drain guide: 12 to 18 inches wide by 18 to 24 inches deep, the only university extension source in our research that gives a full numeric range for a residential French drain rather than a farm-drainage or turf underdrain. NDS, a drainage-products manufacturer, publishes a narrower minimum, 5 to 6 inches wide, for smaller problems; we keep that as a secondary floor. Penn State's Center for Sports Surface Research gives an even smaller 6-by-6-inch trench, but that's a sports-turf underdrain spec, not a yard or foundation drain, so we flag it as a lower-bound cross-check rather than use it as a default.
Pipe slope is the one figure with real agreement. Clemson Cooperative Extension calls for a 1% slope along the trench, and NDS publishes the same 1% minimum (2% for corrugated pipe specifically), with Washington State University Extension and Penn State both citing 0.5% as an acceptable floor. We use 1% as the primary default with 0.5% as the minimum. The commonly repeated "1 inch per 8 feet" shorthand doesn't appear on any extension or manufacturer page we fetched. Do the math and it works out to 1.04%, which lines up with the 1% figure Clemson and NDS publish directly, so we treat it as an equivalent mnemonic, not a citation.
Gravel envelope depth was the least consistent figure in our research. NDS's EZflow installation instructions specify a minimum of 4 inches of permeable backfill around a French drain pipe (6 inches for interceptor and curtain drains), and that's the figure we use, since it's the only one that's unambiguous and manufacturer-attributed. Penn State's turf-drainage spec calls for a similar 4-inch drainage blanket, which we treat as a cross-check. Kirk Allen Landscape Supply publishes 12 to 18 inches below the pipe, an outlier large enough that it reads more like total gravel column height than pipe bedding, so we flag it low-confidence rather than average it in. A third source, NovaConstructionPro, contradicts itself within the same page (3 to 4 inches in one spot, a minimum of 6 inches in another), so we exclude it entirely.
Fabric use is standard practice across every source we checked. LSU AgCenter recommends lining the trench base and walls with geotextile fabric, and NDS wraps its pipe-and-gravel bundles in a 30-sieve geotextile sock. Pipe diameter defaults to 4 inches, the figure NDS, Penn State, and LSU AgCenter all publish for residential use. Whether to use a sock comes down to soil: Michigan State University Extension, writing about agricultural tile drains rather than residential French drains specifically, found that sock-wrapped pipe carries 29% higher inflow than sand-slot pipe and holds up better once clay content at the drain depth drops below 30%, meaning sandier soils are more likely to need one.
No source publishes a ready-made gravel-volume table for French drains, so we derive it: cubic yards per linear foot equals width in feet times depth in feet, divided by 27. Applied to LSU AgCenter's trench range, that runs from 0.0556 cubic yards per linear foot at the smallest dimensions (12 by 18 inches) to 0.1111 at the largest (18 by 24 inches). That matches Kirk Allen Landscape Supply's own worked example exactly, and Kirk Allen's advice to order 10 to 15% extra for settling and compaction is what the calculator adds on top. Installed-cost ranges from Angi ($10 to $100 per linear foot, national average project $9,250) are shown as directional only. The direct fetch of that page was blocked, so the figures come from a search-index summary, not text we read ourselves.
Dehumidifier size calculator
The core sizing table is Energy Star's own buying guidance, used verbatim. At 50 to 75% relative humidity ("slightly to moderately damp"), a small to medium room under 2,000 square feet needs 20 to 30 pints; at 75 to 90% ("very damp"), 25 to 40 pints; at 90 to 100% ("wet"), 30 to 50 pints. Large rooms over 2,000 square feet need at least 30, 40, or 50 pints at those same three conditions. Energy Star's own advice: it's better to oversize than undersize, and if you're replacing an existing unit, you can judge by how much water you empty each day.
A second, more granular table comes from AHAM, the dehumidifier manufacturers' trade association, published on a Perfect Aire spec sheet and recovered through a text-extraction proxy after the PDF itself wouldn't load directly. It breaks room size into 500-square-foot increments across four dampness levels and runs noticeably lower than Energy Star's numbers at comparable areas, for example 18 pints for a 1,500-square-foot moderately damp space versus Energy Star's 20-to-30-pint range for the same condition. We couldn't confirm which side of the 2019 testing change this specific table reflects, and its 2,500-square-foot row returns an identical 26-pint value for two different dampness levels, which breaks the pattern in every other row. We flag that row low-confidence rather than trust it.
The 2019 change is the thing most buying guides get wrong. Starting with products sold in early 2020, the Department of Energy moved the test temperature from 80°F to 65°F, closer to a real basement, which by itself produces a lower pint number for a physically identical unit. Energy Star's own conversion table maps the old ratings to the new ones: an old 70-pint unit maps to a new 40-to-45-pint unit, an old 50-pint unit maps to a new 30-pint unit, and an old 90-pint unit maps to a new 55-pint unit. Retailers use a looser convention that doesn't match that table exactly. Honeywell markets one unit as "50 Pint (70 Pint 2019 DOE Standard)," and Abt lists the same unit as "70 Pint (50 Pint 2019 DOE Standard)." That's a real, widely used label, but it doesn't match Energy Star's own 70-to-40/45 mapping, so we show Energy Star's official conversion as the primary figure and note the retail shorthand as a separate, looser convention.
For target humidity, we use the EPA's own wording from its mold and moisture guide: "If possible, keep indoor humidity below 60 percent (ideally between 30 and 50 percent) relative humidity." That's general indoor guidance, not a basement-specific number. No EPA source in our research singles out basements with their own target, so we apply the whole-home figure to basements as one room among others.
Dehumidifier size calculator →
Electrification rebate checker
Rebate caps come from the HEAR program's statutory table (Inflation Reduction Act Section 50122), as published on Energy Star's partner page and cross-checked against the Department of Energy's own program hub: $8,000 for a heat pump for space heating and cooling, $1,750 for a heat pump water heater, $840 each for an induction stove or heat pump clothes dryer, $1,600 for insulation and air sealing, $4,000 for an electrical panel upgrade, and $2,500 for wiring, with a combined household cap of $14,000 across every appliance. Installers can separately claim up to $500 per project; that doesn't come out of the homeowner's cap.
How much of that cap a household can actually use depends on income relative to its area's median income (AMI), per the same Energy Star page. Households below 80% of AMI can have up to 100% of project cost covered, subject to the caps above; households from 80% to 150% of AMI are capped at 50% of cost; households above 150% of AMI aren't eligible for HEAR rebates at all.
The rule most guides haven't caught up with: on May 29, 2026, the Department of Energy issued Program Notice 26-2, which narrows what HEAR money can pay for. Rebates can no longer fund switching a gas or oil appliance to an electric one, except in new construction; going forward they only cover upgrading an already-electric appliance to a more efficient electric one. States must submit any in-progress fuel-switching projects by August 10, 2026, ahead of an August 31, 2026 deadline for the new rules to take effect (reporting; the underlying DOE notice itself returned unreadable PDF content on our fetch, so it's cited as the primary document but not independently verified). That means a household currently heating with gas who wants a heat pump water heater may no longer qualify for a HEAR rebate on that switch, depending on how far along their state's program is. We surface that caveat rather than compute an eligibility answer the tool can't actually verify.
The parallel Section 25C tax credit is gone. The One Big Beautiful Bill Act, signed July 4, 2025, ended it seven years early: no credit is allowed for any property placed in service after December 31, 2025, per the IRS's own guidance. A household that finished a qualifying install by that date can still claim the 30% credit (capped at $2,000 a year for heat pumps and heat pump water heaters) on a 2025 return, but nothing installed in 2026 qualifies.
HEAR itself is state-administered, not a federal-to-consumer program: each state, territory, and Tribe applies for and launches its own version on its own schedule, and Florida and South Dakota declined their allocation entirely. DOE's dedicated state-by-state tracker page returned a dead link when we checked, so the tool routes to DOE's live program hub instead, which tells users to confirm current status with their state energy office. Rebate rules moved twice in the year we researched this page. We'll update these figures again when they move again.
Electrification rebate checker →
Heat pump water heater payback
Savings figures start with Energy Star's own household-of-4 numbers: about $550 a year in electric bill savings versus a standard electric water heater, more than $5,610 over the unit's service life, and a roughly 3-year simple payback on the price premium, based on 3,760 kWh saved a year. Energy Star also publishes figures for smaller households: 2 people save about $270 a year (5.5-year payback), and 3 people save about $410 a year (3.7-year payback). Those dollar figures assume a fixed electricity rate of $0.146 per kWh and a 13-year equipment life, both dated relative to current prices, so our calculator recomputes the dollar savings from the kWh figures times the electricity rate you enter rather than reusing Energy Star's dollar totals directly.
The default rate is 18.83 cents per kWh, the U.S. Energy Information Administration's national average residential electricity price for April 2026, the most recent month in its published series as of this research. That's up from 15.04 cents in 2022, a roughly 25% rise in four years, and state rates vary enormously around that average, from about 12.35 cents in North Dakota to about 46.62 cents in Hawaii in the same EIA release. We use the national figure as the default and let you override it with your own rate.
Equipment cost assumptions come from two different kinds of sources. Energy Star's own cost breakdown, last dated February 2024 but still consistent with current retailer figures, puts a heat pump water heater's unit cost at $1,500 to $3,000 and installation at roughly another $1,000 to $3,000, for a combined installed cost commonly in the $2,500 to $6,500 range. No federal source publishes a comparable figure for a standard electric water heater, so that baseline, $800 to $1,800 installed, comes from contractor cost-guide sites rather than a government source, and is labeled that way. The calculator defaults to the midpoint of each range, $3,600 for a heat pump water heater and $1,300 for standard electric, with both fields left open for you to enter your own quote.
Heat pump water heater payback →
Corrections
Found a number that doesn't match its source, or a source that's gone stale? Email us at [email protected]. When we can't verify a number, we leave it out.
Yard & Board guides and tools give planning estimates, not professional advice. Building codes and site conditions vary, so confirm structural work with your local permit office or a licensed contractor.