Currency Cross-Rate Converter

Written byOleh Soloninupdated 25 September 2026

Currency

Amount

Source currency rate to the base

What one unit of this currency is worth in your base currency.

Target currency rate to the base

Result

111.11

Cross rate

1.111111

Inverse rate

0.9

In the base currency

$10,000.00

The same amount from target to source

This result is informational only and is not professional advice.

You supply the rates, for the date you need

Converts between two currencies through their rates against a common base, showing the cross rate and its inverse.

Central banks publish every currency against one base. To convert dollars into euros no separate quote is needed: divide one rate by the other and the cross rate falls out.

Rates are entered by hand here on purpose. That keeps the calculation reproducible — you take the official figures for the date that matters, for a report or a contract, and get a result you can later justify.

How to use

Enter the amount in the currency you are converting from.
Enter both rates against the same base — how much one unit of each currency costs on the date you need.
Read the result, the cross rate and the inverse rate; for a report, note the date the rates came from.

Where the cross rate comes from

Most currency pairs have no direct quote, and none is needed. If you know what a dollar costs and what a euro costs in the same base currency, the dollar-to-euro rate is a division: 100 ÷ 90 = 1.1111. That is the cross rate, and it is exactly how banks derive a pair that is not traded directly.

The inverse rate is the same division the other way: 90 ÷ 100 = 0.9. It answers how many dollars are in one euro, and the rate multiplied by its inverse always gives 1.

Why the bureau gives you less

An official rate sits in the middle; a bureau buys below it and sells above it, and the gap between its two prices is its spread. What you lose is how far the rate you are given sits below the official cross rate. On 1,000 units at rates of 100 and 90, a rate three percent worse than the official one costs 33 of the target currency.

Converting 1,000 units at rates of 100 and 90. Worked out with this calculator.
Below the official rate	Rate applied	You receive on 1,000	Lost
0% (official)	1.1111	1,111.11	—
1%	1.1000	1,100.00	11.11
2%	1.0889	1,088.89	22.22
3%	1.0778	1,077.78	33.33
5%	1.0556	1,055.56	55.55

Which rate belongs in a document

Accounting and tax work use an official rate for a specific date, not the one the banking app showed at the time, and which rate and which date is set by the rules of your country. The Bank of Russia, for example, sets its rates on business days to apply from the following day, so a Monday transaction carries the rate set on Friday; the ECB publishes its reference rates at around 16:00 CET for the same day.

Rates are typed in here on purpose. The calculation stays repeatable: a year later the same pair of rates gives the same number, and you can show where it came from — which with an auto-filled live rate would mean noting down the date and the rates separately.

What this calculator shows

The converted amount and the cross rate behind it
The inverse rate — how many units of the source currency make one of the target
The amount in the base currency as the intermediate step

What to keep in mind

Both rates must be quoted against the same base — how much one unit of the currency costs in that base.
Bank spreads and fees are not included; a real exchange lands worse than the official rate by the spread and fees of that particular bank.

FAQs

Where do official rates come from?

The central bank publishes them each working day, effective from the following day. Reporting and contracts use exactly those figures.

What is a cross rate?

A rate between two currencies derived through a third. Direct quotes do not exist for many pairs, so banks compute them the same way — by division.

Why is the bureau's rate always worse?

The spread between buying and selling is how a bureau earns. How far it sits from the official rate differs from one bureau to the next, so for an exact figure use that bureau's own buying or selling rate.

Which rate applies for tax?

The official rate on the date income is received, or on the date of the expense for costs. Interest on a foreign-currency deposit converts on the payment date.

How do I check the cross rate is right?

Check the inputs, not the arithmetic: both rates must be the price of one unit in the same base currency and for the same date. The cross rate times the inverse always gives 1, so that tells you nothing about the rates themselves. A quick test is to compare the result with the cross rate the same source publishes for the pair.

Do both rates have to be against the same currency?

Yes, but which one does not matter. Rates against the dollar, the euro or anything else give the same cross rate, because the shared base cancels out in the division.

Why does my bank quote a different rate?

Banks add a margin to the official rate and often a fee on top. This page works out the clean cross rate without either, which is what you need in order to see how much the exchange is costing you.

Worked example

Dollars into euros

Input: 100 at a dollar rate of 100 ₽ and a euro rate of 90 ₽

Output: 111.11 euros at a cross rate of 1.1111

Note: The inverse is 0.9 — dollars per euro. A real exchange would return less, by that bank's spread and fees.

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