How we calculate
The methods, assumptions and sources behind every 000345 calculator.
Principles
- Geometry is exact: right triangles use the Pythagorean theorem, angles use standard trigonometry, and areas and volumes use standard formulas.
- Material yields (bags of concrete, coverage of paint, densities of gravel) are typical published figures. They vary by product, so we name the assumption on each page and tell you to check the label.
- Code checks (stair risers and treads, for example) use widely adopted residential figures. Local codes differ and always take priority.
- All calculations run in your browser. We don't store the numbers you enter.
Rounding
Lengths in imperial units are shown in decimal feet and in feet-inches to the nearest 1/16". Counts of things you buy (bags, boards, sheets, tiles) are always rounded up.
Review
Each calculator is tested against hand-worked examples, which appear on the page so you can check them yourself. Pages show the date they were last reviewed. Corrections are welcome through the contact page.
Independence
Advertising and sponsorships pay for the site. Sponsors do not see or change formulas, results or editorial conclusions, and paid placements are labelled.
Limits
Calculators help with planning and estimating. They don't replace engineered drawings, permits or inspections. For structural work — foundations, beams, decks, stairs, roofs — confirm with your local building authority and a qualified professional.