OUR APPROACH
Clear formulas.
Confident planning.
Understand the numbers behind your material estimate: from measurements and units to waste allowances and rounding.
From your measurements to a useful estimate.
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01
Measure
Enter dimensions and quantities for your project.
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02
Convert
Bring measurements into compatible units.
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03
Calculate
Apply the formula and your selected allowances.
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04
Explain
Show the result, units, and calculation steps.
The math stays visible.
Each estimate should be easy to follow. Check the formula, confirm your inputs, and see how the result is reached.
- pieces
- 10 pieces
- in thick
- 2 in thick
- in wide
- 6 in wide
- ft long
- 8 ft long
Board feet = (Thickness × Width × Length × Pieces) ÷ 12
2 × 6 × 8 × 10 ÷ 12 =80 board feet
An estimate you can check.
The formula and the units matter just as much as the final number.
Every formula we use, with an example worked by the engine
- Board feetthickness (in) × width (in) × length (ft) ÷ 122 x 6 board, 8 ft long: 8 board feet
- Slab or layer volumelength × width × depth; cubic feet ÷ 27 = cubic yards10 × 10 ft slab, 4 in deep: 33.333 ft³ = 1.2346 yd³
- Roof pitchangle = arctan(rise ÷ run); area multiplier = √(1 + (rise ÷ run)²)6/12 pitch: 26.565°, multiplier 1.118
- Common rafterrun = (span − ridge) ÷ 2; length = run × multiplier, plus overhang24 ft span, 6/12, 1.5 in ridge, 12 in overhang: 14.4646 ft
- Stairsrisers = total rise ÷ target riser, rounded up; treads = risers − 1108 in rise, 7.5 in target riser: 15 risers at 7.2 in, 14 treads
- Weight from volumecubic feet × density (lb per ft³) ÷ 2,000 = US tonsDensity comes from a cited source: Shown once each density is sourced
The details that change your result.
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Units and conversions
Use compatible units before calculating. Switch between imperial and metric while keeping the underlying quantity consistent.
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Material assumptions
Dimensions, density, coverage, and product yield can vary. Use the values specified for your material.
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Waste allowances
Extra material is an adjustable planning choice. Account for cuts, layout, damage, and project complexity.
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Rounding and purchase units
Keep precision during the calculation. Round the final order to the units your supplier sells.
Exact conversion values
| 1 inch | 25.4 mm |
|---|---|
| 1 foot | 12 in = 0.3048 m |
| 1 cubic yard | 27 ft³ |
| 1 board foot | 144 in³ |
| 1 pound | 0.45359237 kg |
| 1 US ton | 2,000 lb |
An estimate is a starting point.
Confirm dimensions, product specifications, and site conditions before ordering. Structural or code-related decisions need qualified professional advice.
- Check supplier specifications
- Confirm site measurements
- Review local requirements
Where the numbers come from.
Good estimates start with appropriate references.
- Geometry and unit definitionsStandard formulas for area, volume, length, and unit conversion.
- Manufacturer specificationsProduct-specific coverage, bag yields, densities, and installation guidance.
- Published technical guidanceRelevant reference material, with context for assumptions and limitations.
Check the individual calculator for the references and assumptions that apply.
Material figures on file
Each figure is stored with its source and the date we last checked it. The site will not build without them.
- Hardwood lumber, thickness and tally rulesAmerican Hardwood Export Council (AHEC), Grading sawn lumber: Measurement checked 9 November 2026Hardwood Industries, Board Footage Calculator notes (NHLA length rule, quarter thickness) checked 9 November 2026
- Softwood dimension lumber, minimum dressed dry sizesNIST, Voluntary Product Standard PS 20-25, American Softwood Lumber Standard (effective January 2025; supersedes PS 20-20 with unchanged dressed sizes), Table 3 checked 9 November 2026
Questions about the calculations.
Why can my result differ from a supplier quote?
Supplier sizing, product yields, minimum order quantities, waste, taxes, and delivery can change the final order or price. Our result is the quantity your measurements call for; a quote is what a supplier will sell you.
When should I use actual dimensions?
Use actual dimensions when the real size matters, such as fitting boards into a space or working out coverage. Use nominal sizes when your supplier prices by them, as most lumber yards do for board feet.
How should I choose a waste allowance?
Base it on the job. More cuts, angles, offcuts, and lower grades mean more waste. The calculators start at 0% so you set the allowance yourself, and it is added once, at the end, where you can see it.
Why are some results rounded up?
Bags, sheets, boards, and bricks are sold whole. We keep full precision through the math, add waste, then round those items up so you do not come up short.
Spotted something that needs a closer look?
Send the calculator name, your inputs, and the result you expected so the calculation can be reviewed. Fixes go into the formula and its test cases, so the correction reaches every page and the app at once.
Help make the tools clearer.