Calculator methodology

HandyNumbers is designed to make everyday calculations transparent. We show the formula or method on calculator pages so you can understand what the result represents.

How calculations are checked

Calculators are tested against worked examples and common edge cases such as zero values. Where a calculation depends on assumptions, those assumptions are stated on the page.

Estimates versus official figures

Some subjects—such as lending, tax, towing, electricity tariffs and vehicle costs—depend on rules, rates or circumstances that can change. HandyNumbers results are general planning estimates and do not replace a quote, contract, official source or professional advice.

Corrections

If you spot a calculation problem or unclear explanation, email hello@handynumbers.com. Useful corrections are reviewed and incorporated into the relevant calculator.