Calculation methodology
Transparent formulas and assumptions so you can check every result.
Currency conversion formulas
Let R be the number of foreign-currency units per one US dollar. For a fee-free conversion: foreign amount = USD amount × R; USD amount = foreign amount ÷ R. R must be positive.
Fee model
For the optional fee estimate, the percentage fee is calculated from the original source amount: percentage fee = source amount × fee% / 100. Then net source amount = source amount − fixed fee − percentage fee. The net source amount is converted at the entered rate. If fees exceed the source amount, the calculator reports an error instead of a negative payout.
The fixed fee is denominated in the source currency. This is a simplified comparison model, not a promise of how any particular provider calculates fees. The tool does not independently estimate a hidden exchange-rate spread.
Quote comparison and precision
For two rates A and B, each quoted as foreign units per USD, the difference in foreign units is USD amount × (A − B). Calculations use JavaScript numeric precision. Displayed results are rounded for readability; a provider may apply currency-specific minor-unit rules and rounding at intermediate stages.
Data sources and freshness
No external rates are fetched. You must supply your own quoted rate. Currency names and symbols are display conveniences, not evidence of a current rate. No exchange-rate provider is endorsed, and no transaction is executed on this site.
Limitations
Quoted prices can vary with timing, order size, settlement method, intermediary institutions, and customer eligibility. Tax and reporting requirements may apply to some transactions. Confirm final terms with your provider.
Reproducing and checking a result
Write down your input amount, the currency units in the rate, any source-side fixed charge, and any source-side percentage. Compute the net source amount using the assumptions displayed beside the tool. Convert that net amount by multiplying or dividing according to the selected direction. Compare the unrounded intermediate result with the displayed output, allowing for currency rounding.
Fee-order example
For $1,200 with a 1% source-side fee and a $4 fixed source-side fee, the modeled net amount is $1,200 − $12 − $4 = $1,184. At a hypothetical 0.91 EUR per USD, the result is €1,077.44. A provider that charges fees after conversion may give a different answer even when the nominal fee amounts appear similar.
Rate spread calculation
For a reference rate R and customer rate C quoted in the same direction, a simple relative difference is (R − C) ÷ R × 100%. If R = 0.92 and C = 0.90, the customer rate is approximately 2.17% below the reference. This comparison is informative but does not establish a universal fee percentage for all transaction directions.
Accuracy and rounding
Do not round the rate before the conversion if the provider supplies more digits. Small rounding differences can become noticeable on large transfers. Currency display precision also varies; Japanese yen are commonly shown without decimal fractions while many other currencies display two decimals. The calculator is intended for estimating, not final settlement accounting.
Why no live-rate claims appear here
The site does not operate a market-data feed or verify the age of the rate you type. A user-entered quote remains a user-entered quote even if a date is supplied. To obtain a current quote, consult a bank or established exchange-rate provider, then use this tool to understand its arithmetic and assumptions.