How We Check Our Numbers

Every calculator on Measure Twice is built to be checked. This page explains how.

One question per page

Each calculator answers a single practical question, such as how much paint a room needs or how many bags of concrete fill a post hole. The page shows the formula it uses, a worked example and the assumptions behind it, so you can follow the math yourself.

Where the figures come from

Coverage rates, yields, densities and waste allowances come from product labels, manufacturer technical data and established trade rules of thumb used in the United States, Canada and Australia. Where products differ, the calculator lets you enter the figure printed on your own product, and the page says so.

Testing

Before a page is published, its formulas are run against the worked examples and every number quoted in the text, in both imperial and metric units. If a number in the text does not match the calculator, the page is not published until it does.

Safety and codes

Where a project involves structure, electricity, gas, heights or carbon monoxide, the page says so plainly and points you to local building codes and qualified professionals. Our results are estimates for planning and shopping, not engineering designs.

Updates and corrections

Each page shows the date it was last updated. If you find an error, email hello@measuretwiceguide.com with the page address and the values you entered. We check every report and correct confirmed mistakes.

Advertising

The site is supported by advertising. Advertisers have no influence on the content, and ads never change a calculator's results.