Currency Exchange Fee Calculator
r = target per source (or reciprocal of the entered reverse quote). G = A × r. Percentage fee = G × p / 100, expressed in the chosen fee currency; fixed source fees multiply by r. F is the sum in target units. Deduct: N = G − F, debit = A; separately: N = G, debit = A + F / r. Unrounded inverse: A = (desired N + fixed target fees) / [r × (1 − sum(p)/100)] for deduct, or desired N / r for separate fees. Displayed effective rate = N / debit. All rows retain exact rational values before fee rounding.
r = target per source (or reciprocal of the entered reverse quote). G = A × r. Percentage fee = G × p / 100, expressed in the chosen fee currency; fixed source fees multiply by r. F is the sum in target units. Deduct: N = G − F, debit = A; separately: N = G, debit = A + F / r. Unrounded inverse: A = (desired N + fixed target fees) / [r × (1 − sum(p)/100)] for deduct, or desired N / r for separate fees. Displayed effective rate = N / debit. All rows retain exact rational values before fee rounding.
Local decimal arithmetic uses reduced BigInt fractions, not floating-point money. Plain signed decimals only (no exponent): at most 80 digits and 30 decimal places. Up to 30 scenarios, 100 items per scenario, Rooms/nights are positive whole numbers; points are nonnegative whole numbers. Percentage fees/taxes are nonnegative, with no business upper cap. Names 1–120 characters; currency labels 1–24. Result fractions have a 4,096-digit resource limit. Tables show exact terminating decimals, otherwise the exact numerator/denominator; no guessed currency precision. Empty required values are rejected. Optional blank reference/tax means omitted; blank quantum means no rounding. No external data or network request.
Results
A QUICK WALKTHROUGH
How to use this tool
- Name scenarios and enter a common currency label.
- Fill every required amount and explicitly select each item’s model.
- Select a baseline, calculate, and review every result and the full report.
Formula
r = target per source (or reciprocal of the entered reverse quote). G = A × r. Percentage fee = G × p / 100, expressed in the chosen fee currency; fixed source fees multiply by r. F is the sum in target units. Deduct: N = G − F, debit = A; separately: N = G, debit = A + F / r. Unrounded inverse: A = (desired N + fixed target fees) / [r × (1 − sum(p)/100)] for deduct, or desired N / r for separate fees. Displayed effective rate = N / debit. All rows retain exact rational values before fee rounding.
Limits
Local decimal arithmetic uses reduced BigInt fractions, not floating-point money. Plain signed decimals only (no exponent): at most 80 digits and 30 decimal places. Up to 30 scenarios, 100 items per scenario, Rooms/nights are positive whole numbers; points are nonnegative whole numbers. Percentage fees/taxes are nonnegative, with no business upper cap. Names 1–120 characters; currency labels 1–24. Result fractions have a 4,096-digit resource limit. Tables show exact terminating decimals, otherwise the exact numerator/denominator; no guessed currency precision. Empty required values are rejected. Optional blank reference/tax means omitted; blank quantum means no rounding. No external data or network request.
Full exact report
You supply every amount, rate, fee and currency label. This tool calculates only; it does not look up prices, exchange rates, taxes or rewards.
Fee rounding
Inverse solves the unrounded fee model. Quantum rounding is applied afterward; the displayed shortfall must be checked. The result is not a bank quote or a guaranteed rounded minimum. Target not met; adjust source amount using the forward calculation
GOOD TO KNOW
Common questions
Where do prices and rates come from?
You supply every amount, rate, fee and currency label. This tool calculates only; it does not look up prices, exchange rates, taxes or rewards.
Are the report values rounded?
Local decimal arithmetic uses reduced BigInt fractions, not floating-point money. Plain signed decimals only (no exponent): at most 80 digits and 30 decimal places. Up to 30 scenarios, 100 items per scenario, Rooms/nights are positive whole numbers; points are nonnegative whole numbers. Percentage fees/taxes are nonnegative, with no business upper cap. Names 1–120 characters; currency labels 1–24. Result fractions have a 4,096-digit resource limit. Tables show exact terminating decimals, otherwise the exact numerator/denominator; no guessed currency precision. Empty required values are rejected. Optional blank reference/tax means omitted; blank quantum means no rounding. No external data or network request.
Theoretical source amount (unrounded model)?
Inverse solves the unrounded fee model. Quantum rounding is applied afterward; the displayed shortfall must be checked. The result is not a bank quote or a guaranteed rounded minimum. No inverse: nonpositive coefficient; zero coefficient is nonunique only when the target equals the constant net, otherwise impossible. Negative coefficient gives no admissible nonnegative source for nonnegative target and fees. Target not met; adjust source amount using the forward calculation