Currency Converter: ECB Daily Reference Rates
Convert between USD, EUR, GBP, JPY and six more at the European Central Bank's daily reference rate, with the date the rate was published for.
Currency Converter
Rates come from the European Central Bank euro foreign exchange reference rates, republished by frankfurter.dev. The endpoint and the response were checked on 2026-09-06.
A reference rate is not a price anyone can trade at. A bank, a card or a money transfer will use its own rate and add its own fees, so the figure here is a guide rather than what a payment will cost.
Documentation
A currency converter turns an amount of money in one currency into the matching amount in another currency, using an exchange rate. This one converts between ten major currencies at the European Central Bank's daily reference rate, and shows the date that rate was published for.
How the currency converter works
The tool takes three inputs: an amount, the currency the amount is in, and the currency to convert it to. It then asks a rate feed for the most recent published rate for that pair, multiplies, and rounds the answer to the number of decimal places the target currency actually has.
Ten currencies are offered: USD (US dollar), EUR (euro), GBP (pound sterling), JPY (Japanese yen), CNY (Chinese yuan), CHF (Swiss franc), CAD (Canadian dollar), AUD (Australian dollar), HKD (Hong Kong dollar) and KRW (South Korean won).
The amount can be from 0 up to 1,000,000,000,000 units. A checkbox switches the tool to a rate typed by hand, which must be above 0 and no higher than 1,000,000,000. That field is the override for anyone who was quoted a different rate, and it opens on its own when the feed cannot be read.
Currency conversion formula
An exchange rate is the number of units of the target currency that 1 unit of the source currency buys. A rate of 0.86044 for US dollars to euros means 1 US dollar buys 0.86044 euros.
The converted amount is the amount times the rate, rounded once at the end:
where C is the converted amount, A the amount in the source currency, R the exchange rate, and d the number of decimal places the target currency has.
Rounding once matters. Rounding the rate first, or rounding a part-way total, prints a figure that does not equal the amount times the rate.
The tool also shows the same rate read the other way round, which is how many source units 1 target unit buys:
where R' is the reverse rate.
Worked example
The reference rate published for 4 September 2026 for US dollars to euros was 0.86044. Converting 100 US dollars gives 100 times 0.86044, which is 86.044, and rounding to the two decimal places the euro has gives 86.04 euros.
The same day, the rate for euros to US dollars was 1.1622, so 100 euros comes to 116.22 US dollars. A computer stores 1.1622 as the nearest binary fraction, so the product actually lands on 116.21999999999998. Rounding that product to two decimal places gives 116.22. Cutting the extra digits off instead would give 116.21.
The rate for US dollars to Japanese yen was 156.25, so 100 US dollars comes to 15,625 yen. That figure has no decimal part, because the yen has no subdivision.
Where the rates come from
| Publisher | European Central Bank |
| Series | Euro foreign exchange reference rates |
| Feed | frankfurter.dev, which republishes that series |
| Published | Once each working day, at around 16:00 Central European Time |
| Endpoint last checked | 6 September 2026 |
The published rates are at ecb.europa.eu, and the feed that republishes them is at frankfurter.dev. The rates quoted in the example above were the ones published for 4 September 2026, read from that feed.
No rate is written into the tool's code. A rate fixed at build time would be wrong on the next working day, and would then keep showing a number that looks current. The rate arrives with the day it belongs to, and that day is shown next to the result.
Currencies without cents
ISO 4217, the standard that assigns currency codes, also gives each currency a minor unit: how far it divides. Eight of the ten currencies here divide into hundredths, so their amounts carry two decimal places. The yen and the won do not divide at all, so their amounts are whole numbers.
The rule applies to the amount that is typed as well as to the answer. An amount of 100.7 yen is read as 101 yen before anything is multiplied, so the amount on the page and the amount that was converted are the same figure. At the rate published for 4 September 2026 for yen to US dollars, 0.0064, that 101 yen comes to 0.6464, which rounds to 0.65 US dollars.
What the converter cannot know
The answer is an estimate of what an amount is worth, not a price. Several things sit between the two.
A reference rate is not a rate anyone can trade at. The European Central Bank publishes the set for information. A bank, a card network or a money transfer service uses its own rate, usually a little worse, and adds its own fees. The real cost of a payment is therefore higher than the figure here, and the tool has no way to know by how much.
The set is published once each working day. It does not move during the day, and there is no new set at weekends or on days the bank is closed, so the most recent published rate can be a few days old. The tool shows no historical rates and no trend.
Very large inputs are refused rather than answered. The largest allowed amount at the largest allowed hand-entered rate comes to 1 followed by 21 zeros, and a computer cannot hold a number that big down to the last cent. When a product is past that limit the tool says so and shows no figure.
If the feed cannot be read, for any reason, no number is shown at all. A stale or invented rate is never displayed.
Frequently asked questions
Why is the amount here different from what a bank pays out?
Banks and transfer services do not use the reference rate. They set their own rate, which is usually a little less favourable, and they may add a fixed fee or a percentage. The difference between the two rates is a cost even when the service says it charges nothing.
How often does the rate change?
Once each working day. The European Central Bank publishes the reference rates at around 16:00 Central European Time. There is no update at weekends or on holidays, so on a Sunday the rate shown is Friday's.
Why does a yen amount have no decimal places?
Because the yen has no smaller unit. ISO 4217 gives the yen and the won a minor unit of zero, so an amount in either is a whole number. Writing 15,625.00 yen would claim a precision the currency does not have.
What happens when the rate feed cannot be read?
The tool says the rate could not be read and opens a field for a rate typed by hand. It does not fall back to an older rate. The same field can be used at any time to check an amount against a rate quoted elsewhere.
Why is the reverse rate not the full result of the division?
The published rate carries five or six digits. Dividing 1 by 0.86044 produces 1.16219608 and more, but only 1.1622 is supported by the data behind it. The extra digits come from the division, not from the European Central Bank. The tool prints the reverse rate at the fewest decimal places that read back to the rate above it, which is the same figure the feed itself publishes for the reverse pair.