Useful numbers need context.

FreeToolCalc publishes calculators and practical explanations for everyday planning. A result is only as useful as the inputs and assumptions behind it. This page sets out the standards we use when creating or revising a tool.

Explain the calculation

A tool should make its units clear, describe its purpose, and explain the assumptions that change the result. Where a worked example is included, it should use the same method as the calculator. We avoid assigning a generic formula to a tool just because it belongs to a similar category.

Separate an estimate from a promise

A savings projection assumes a rate; it cannot know future returns. A material estimate depends on coverage and waste. A health screening number does not assess an individual’s health. Read the tool’s limitations before using a result for a decision.

Use sources that explain the method

For sourced health and financial explanations, we prefer the organization responsible for the guidance, such as a public health body or consumer regulator. A source link is not an endorsement of this website. We do not claim that the tools have been independently certified or professionally reviewed.

Write for the task

Explanations should help you enter your figures, check a result, or understand a limitation. We do not treat a word count, a year in a title, or repeated keywords as a substitute for useful information. Content may be prepared with software assistance; the site does not present a fictional expert as its author.

Report a problem

If an answer looks wrong, please contact us with the calculator address, your inputs and units, the result shown, and the result you expected. Avoid sending personal or sensitive information. This makes it easier to reproduce the issue and correct the calculation or its explanation.