Precision and rounding
Calculations use full JavaScript numeric precision internally. Display rounding is applied only when a result needs readable currency, percentages, or units.
Trust & accuracy
Calculation Methodology
The shared rules behind precision, rounding, money, interest, units, dates, health estimates, testing, and privacy.
Money
Currency results are estimates. Fees, taxes, compounding frequency, payment timing, and locale-specific rules are stated on the relevant page.
Interest
Interest tools distinguish nominal rates, effective rates, compounding frequency, contribution timing, and amortized payments.
Units
Conversions use explicit conversion factors. Unlike dimensions are not converted without the missing measurement—for example, area to linear length requires material width.
Dates and time
Date tools identify whether endpoints, weekends, holidays, time zones, or daylight-saving changes affect the result.
Health
Health outputs are screening estimates based on named methods, not diagnoses. Limitations and appropriate disclaimers accompany the result.
Reference vectors
Changed calculators are exercised against known examples and invalid inputs, then rechecked in the production browser under the deployed Content Security Policy.
Privacy
Calculator values stay in the browser unless a page clearly labels an external data request. Analytics events must not include calculator inputs or results.
Methodology reviewed: July 2026