Currency Converter
Convert between currencies with clear rounding.
Results
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How the currency converter works
A rate is the price of one unit of the base currency expressed in the quote currency. Because of that, converting is a multiplication. For a direct quote the formula is converted = amount * rate, and the result is rounded to the quote currency’s minor unit (the number of decimal places it uses) at the very end.
When neither side of the pair is the pivot currency, the converter uses a cross rate. It triangulates through a common pivot (usually USD) with converted = amount / ratePerUsdFrom * ratePerUsdTo. Each per-USD rate is the number of that currency’s units per one US dollar. Dividing by the source rate recovers the dollar value, and multiplying by the target rate re-prices it. The full-precision intermediate value is carried all the way through, and rounding happens only once, at the final step, so chained steps do not compound rounding error.
Worked example
Convert 500 GBP to JPY. Suppose the market quotes 0.79 GBP per USD and 157 JPY per USD. JPY has zero decimal places.
- Recover the USD value:
500 / 0.79 = 632.911...USD - Re-price in yen:
632.911... * 157 = 99,367.0886... - Round to JPY’s minor unit (0 decimals): 99,367 JPY
If instead you converted 250 EUR to USD at a direct rate of 1.0832 USD per EUR:
| Step | Value |
|---|---|
| Amount | 250 EUR |
| Rate | 1.0832 USD per EUR |
| Raw product | 270.80 |
| Rounded (2 decimals) | 270.80 USD |
The rounding rule is half away from zero, so a result ending in exactly half a cent rounds up.
How to use it
- Pick the from and to currencies, then enter the amount you hold in the source currency.
- Accept the pre-filled rate for a quick estimate, or paste a specific rate from your bank, broker, or invoice to model a real transaction.
- Read the result in the target currency’s natural precision: cents for most currencies, whole units for yen and won.
- To check a fee, convert at the mid-market rate, then compare against the amount your provider actually quotes. The gap is the spread plus any flat fee.
Limitations
This tool does the arithmetic of a conversion cleanly, but it does not model the cost of an actual transfer. Real exchanges add a spread to the mid-market rate, may charge a fixed fee, and can apply a different rate for buying versus selling. Card transactions abroad may also carry a foreign-transaction fee set by your issuer. Rates move continuously, so a figure that is correct now can be stale within minutes. Treat the output as an estimate for planning and comparison, not as a guaranteed price or as financial advice.
Frequently asked questions
Does this use live exchange rates?
The converter fills in a current market rate for the pair you pick, and you can also type in your own rate. The math itself does not depend on where the rate comes from, so a rate you paste from your bank or a contract works exactly the same way.
Why does the converted JPY amount have no decimals but USD has two?
Each currency has a minor unit. The US dollar splits into 100 cents, so it shows two decimal places. The Japanese yen and Korean won have no sub-unit in practice, so they round to a whole number. The converter rounds the result to the target currency's minor unit, not the source currency's.
Is the rate my bank gives me the same as the rate shown here?
Usually not. Banks and card networks add a margin (a spread) and sometimes a flat fee on top of the mid-market rate. The figure here is a clean reference rate, so expect a real transfer to land a little below it after costs.
How is a cross rate between two non-USD currencies calculated?
It triangulates through a pivot currency, normally USD. The amount is divided by the source currency's per-USD rate to recover the USD value, then multiplied by the target currency's per-USD rate. Rounding happens once at the very end, so the intermediate USD figure keeps full precision.
Does converting back and forth return my exact starting amount?
Not always to the last unit. A single direct conversion at a given rate is exact, but rounding to the target minor unit and then converting back can leave a difference of one minor unit. This is normal and is the cost of presenting clean, spendable figures.