Disclaimer

Estimates, not advice

Every figure on this site is an estimate for planning a job. It is not engineering advice, building advice, or professional advice of any kind. Nothing here has been prepared for your particular site, ground conditions, structure or jurisdiction.

No warranty of accuracy

The formulas are published on each calculator page so you can check them, and each page states the assumptions it makes. Even so, we do not warrant that any result is accurate or fit for your purpose. Material properties vary between products and batches, site conditions vary, and workmanship varies. Two people following the same number can need different quantities.

Confirm quantities with your supplier before ordering. A supplier knows the yield, coverage and density of the product they are actually selling you; we work from typical published figures.

Building codes and safety

Thickness, depth, reinforcement, spans, stair dimensions and much else are regulated, and the rules differ by country and jurisdiction. Where a calculator mentions a typical figure it is a rule of thumb, not a code requirement, and we never describe a result as code compliant. Check your local building code, and consult a qualified professional for anything structural.

No liability

To the fullest extent the law allows, we accept no liability for any loss arising from use of this site, including materials bought, work carried out, or decisions taken on the basis of a result shown here. If you are not willing to verify a figure before spending money on it, please do not rely on it.

Telling us about a problem

If a calculator gives an answer you believe is wrong, we want to know. Every calculator page has a link to report a problem, and it helps enormously if you say which calculator, what you entered and what you expected.