Formula-first approach
Each calculator is based on a stated mathematical formula. The formula appears on the calculator page alongside worked examples so the result can be checked independently.
Rounding and display
Calculations use JavaScript number arithmetic in the browser. Results are displayed with up to six decimal places where needed, while integers and short decimals remain easy to read. Very large, very small or high-precision financial calculations may require specialist decimal arithmetic beyond the scope of this general-purpose site.
Input validation
PercentWise blocks undefined operations such as dividing by zero and adds context-specific checks where a percentage or weight has a meaningful range. If an input combination does not produce a valid result, the calculator explains what needs to change.
Privacy by design
The numbers typed into calculators are processed locally in the browser. PercentWise does not send calculator input values to its server. Google Analytics is configured separately for aggregate site usage and follows the analytics preference described on the Privacy page.
Rates, rules and real-world decisions
Tax, VAT, payroll and academic rules vary by location and institution. PercentWise calculators are general mathematical tools, not legal, tax, financial or academic-policy advice. Where a rate or rule matters, verify it with the relevant official source.
Corrections
If a result or explanation appears wrong, email [email protected] with the calculator name and the values used. Reports can then be reproduced and checked.
Methodology reviewed: 22 October 2026