How We Build Our Calculators

Every Calcvera calculator follows the same process before it is published. This page explains it, so you can judge how far to rely on our results.

1. Standard formulas, shown on the page

We use the standard method lenders and textbooks use for each calculation, and every calculator has a "How this is calculated" box with the exact formula. For example, our loan calculator uses the standard amortisation formula, with a monthly rate of APR รท 12.

2. Full precision, rounded only for display

Calculations run at full precision. We round only when we show a figure, to the nearest cent or penny. On a loan, the final payment is adjusted so the balance ends at exactly zero. Lenders who round each payment first may differ from us by a few cents or pence in total.

3. Tested against known answers

Each calculator's maths is covered by automated tests with known correct answers, including edge cases such as a 0% interest rate, a one-month term, extra payments and very large values. We also compare at least three results with a trusted independent calculator before publishing, and the tests run again before every update goes live.

4. Official sources for every tax figure

We take tax bands, allowances and legal limits only from official government sources:

Every tax calculator shows which tax year it uses.

5. Updated when the rules change

We review each country's figures when its tax year changes: the US and Canada in January, the UK in April and Australia in July. Each guide shows the date it was last updated.

6. Your data stays on your device

Calculations run in your browser. The numbers you enter are never sent to us. See ourPrivacy Policy.

Found a mistake?

Please tell us. We check every report and fix confirmed errors as a priority.