Calculation Methodology
Our aim is to make each calculation understandable and repeatable. The formula and assumptions are published alongside the tool.
Inputs and validation
Numeric inputs must be finite and within the tool’s limits. Empty fields do not silently become zero. Ratios cannot divide by zero, dates must be valid, and absolute temperatures cannot fall below absolute zero.
Precision and rounding
Calculations use JavaScript floating-point arithmetic. Results display up to six decimal places; display rounding does not change the underlying calculation. This is not an exact-decimal accounting system. Verify currency amounts and contractual payments independently.
Dates and units
Age calculations use the Gregorian calendar and date-fns calendar functions. February 29 anniversaries use February 28 in non-leap years. Unit conversions use explicit factors: a foot is 0.3048 metres and a pound is 0.45359237 kilograms.
Financial assumptions
Loan payments assume a fixed nominal annual rate, monthly payments, and no fees. VAT uses your entered rate rather than a country default. Salary conversion estimates gross pay from your schedule. Profit margin is gross, not net.
Testing
The project includes automated examples and boundary checks for calculator logic, plus browser checks for URL restoration, language direction, and responsive layouts. Tests reduce mistakes but cannot guarantee suitability for every use.