Exchange-Rate Methodology
Calculations use integer-scaled rates and explicit formulas so displayed values remain consistent across the calculator, API, tables, and charts.
Content reviewed Jul 13, 2026
Spot and cross rates
Rates are mid-market reference values. When a direct pair is unavailable, a cross rate is derived from stored USD legs: USD-to-target divided by USD-to-source. Reverse rates are calculated by inversion.
Precision
Rates are stored as scaled integers at 1e8 precision. Monetary conversions use integer arithmetic at the calculation boundary; JavaScript numbers are used only for display and statistical charts.
Historical observations
History pages use stored daily market observations ordered by UTC market date. Range controls slice the same series without changing the underlying observations.
Expected ranges
The expected-range chart uses exponentially weighted daily log-return volatility, annualized and widened over time using the square-root-of-time convention. It is a descriptive ±1σ range, not a price forecast.
Limitations
Market gaps, provider delays, illiquid currencies, and customer spreads can make an executable rate differ from the reference shown. Past variation does not predict future direction.