How we check our calculators

1. 1.

   Source the method. We use standard definitions or a named published formula.

2. 2.

   Test with known answers. Each tool is run against worked examples, such as 100 °C = 212 °F or a 30-year $280,000 loan at 5.5% costing $1,589.81 a month.

3. 3.

   Show the working. You can see every step, so you can check it yourself.

4. 4.

   Re-check on a schedule. Tools are reviewed regularly and the review date is shown on the page.

5. 5.

   Fix reported errors. If you tell us about a mistake, we investigate and correct it.