Updated
Editorial policy
Every CalculatorJam calculator follows the same rules. Today that means the percentage, tip, age and final grade calculators.
- Documented formulas. Each page states its formula and shows the work with your numbers substituted. Nothing is a black box.
- Automated reference tests. Every calculation is verified against independently hand-computed reference values, including edge cases (leap days, month-end dates, half-cent rounding, impossible grade targets), before any change ships.
- Stated conventions. Where math has more than one defensible convention (month-end age counting, Feb-29 birthdays, per-person rounding), the page says which one it uses and why.
- Stated limits. Each tool publishes its supported input ranges and its display precision.
- Visible dates. Every calculator page shows when it was last updated.
- No dark patterns. No email capture, no lead-generation forms, no sign-up walls. Ever.
Found an error? We treat correctness reports as the highest-priority work. A correction updates the page and its visible date.