How we calculate

Every calculator on Honest Calculators shows the formula it uses and a worked example, so you can check the answer yourself.

Standard formulas, tested

We use the standard published formulas for each calculation — for example the fixed-rate loan payment formula, compound interest using the quoted APY, and the definitions of percentage change. Each formula is covered by automated tests that check the results against independently worked examples, and those tests run before any change goes live.

Assumptions

Each page lists its assumptions. Common ones: rates stay fixed for the period shown, payments are made monthly and on time, and deposits are made at the end of each month. Real accounts and loans can differ — variable rates, fees, rounding conventions and day-count methods all affect the exact figures.

Reviews and updates

Each calculator shows when it was last reviewed. Calculators that depend on rules that change — such as tax brackets or contribution limits — are reviewed for each new tax year.

Privacy

Calculations run in your browser. The numbers you enter are not sent to us; they only appear in the page address so you can bookmark or share a result.

Not advice

Results are estimates for information and education. They are not financial, tax, legal or medical advice. For decisions that matter, confirm figures with your lender, bank or a qualified professional.