Best Exchange Rate API for the USA in 2026: 8 Compared for USD Rates, Treasury, Fed and IRS Tables

A US product usually needs two different things from an exchange rate API. The app needs a live dollar rate for pricing, checkout or a dashboard. The finance side needs the specific table a US form names: the Treasury year-end rate for the FBAR, a Federal Reserve rate for a transaction date, an average for the year. Most APIs do the first and not the second.

This comparison looks at eight exchange rate APIs from the point of view of a team in the USA. Free-tier limits and prices were read from each provider's own pricing page on 10 November 2026; they change often, so confirm before you commit.

What a team in the USA needs from an exchange rate API

• Live USD pairs for pricing and conversion, refreshed often enough for checkout.
• Treasury Reporting Rates of Exchange, the quarterly table that the FBAR and Form 8938 instructions point to for the year-end value.
• Federal Reserve H.10 daily rates for transaction-date conversions and for computing averages.
• IRS yearly average rates for income received evenly through the year.
• History by date, because every one of those uses is a lookup for a past date.

Quick comparison

The US tables and what they are for

• Treasury Reporting Rates of Exchange. Quarterly, dated 31 March, 30 June, 30 September and 31 December, with amendments when a rate moves 10% or more. The Form 8938 instructions say that in most cases you must use the Treasury Bureau of the Fiscal Service rate on the last day of the tax year, and the FBAR instructions point to the same Treasury year-end rate.
• Federal Reserve H.10. Daily noon buying rates in New York for 23 currencies, released weekly on Mondays for the previous business week. The usual source for the rate on a specific transaction date.
• IRS yearly average rates. A table of calendar-year averages. The IRS states that it has no official exchange rate and generally accepts any posted rate used consistently, so this table is a convenience, not a requirement.

The point for choosing an API: a market mid-rate and an official table are different products. A market rate is right for showing a customer a price. It is not the figure a tax form or an auditor asks for.

The eight providers

1. AllRatesToday

Best for: teams that need both kinds of rate. Mid-market rates for 160+ currencies refresh every 60 seconds on every plan, on any base currency, over HTTPS. The same key serves the official tables of 123 central banks and 6 tax authorities, each with the publisher's own date. For the USA that means: Treasury, Fed H.10 and IRS. Output is JSON, CSV, XML or Excel from the same endpoints, with SDKs for JavaScript, Python, PHP, Go and Rust and an MCP server for AI agents. Paid plans start at €4.99 a month; dated tables and history are on paid plans.

2. Frankfurter

Best for: projects that only need official fixings and want them free. Frankfurter is open source, needs no key and has no monthly cap. It now aggregates 111 central banks and official sources. For the USA its source list covers: Treasury and Fed (via FRED); no IRS table. It serves official fixings, not a live market rate, and it is a free service with no paid tier or support contract.

3. ExchangeRate-API

Best for: dashboards and reports that need volume and can live with one update a day. The free plan gives 1,500 requests a month with daily updates; the Pro plan is $10 a month for 30,000 requests with hourly updates. Rates are a blended market figure, not a named institution's table.

4. Open Exchange Rates

Best for: teams that want a long-established vendor and work from a US dollar base. The free plan gives 1,000 requests a month with hourly updates on a USD base; other base currencies start with the $12 a month plan.

5. CurrencyAPI

Best for: small private projects. The free plan gives 300 requests a month with daily updates and is for private use only; paid plans start at $12.99 a month.

6. Fixer

Best for: teams already on the apilayer marketplace. The free plan gives 100 calls a month with hourly updates for non-commercial use, and base-currency switching is listed only on paid plans, which start at $14.99 a month.

7. currencylayer

Best for: the same apilayer stack with a dollar source. The free plan gives 100 calls a month with daily updates for non-commercial use; paid plans start at $14.99 a month.

8. XE Currency Data

Best for: banks and large companies that need a recognised vendor on an annual contract. There is a trial but no free plan; the entry plan is $599 a year for 10,000 requests a month with daily rates.

Try it for USD

# live mid-market rate
curl "https://allratestoday.com/api/v1/rates?source=EUR&target=USD" \
  -H "Authorization: Bearer YOUR_API_KEY"

# the Treasury table in force
curl "https://allratestoday.com/api/open/central-bank/ustreasury"

# Federal Reserve H.10, latest release
curl "https://allratestoday.com/api/open/central-bank/fed"

The first call needs a free API key. The official table responses carry the table's own date, so you can show which publication a figure came from.

Which one should you pick?

FAQ

What is the best exchange rate API for US businesses in 2026?

It depends on the job. For live USD rates plus the Treasury, Federal Reserve and IRS tables on one key, AllRatesToday. For free daily official fixings with no key, Frankfurter. For the largest free quota of daily market rates, ExchangeRate-API.

Which API has the Treasury reporting rates for the FBAR?

AllRatesToday serves the Treasury Reporting Rates of Exchange by reporting date, with amendments handled, and Frankfurter lists the US Treasury among its sources. Market-rate APIs such as Open Exchange Rates, Fixer and currencylayer do not serve the Treasury table.

Is there a free exchange rate API with USD as the base currency?

Yes. AllRatesToday, Frankfurter, ExchangeRate-API and CurrencyAPI allow any base on their free tier, and Open Exchange Rates' free plan is USD-based by default.

Does the IRS have an official exchange rate API?

No. The IRS says it has no official exchange rate and publishes a yearly average table as a web page. AllRatesToday serves that table as JSON.