US dollar (USD) exchange rate API

The US dollar is the currency most foreign exchange trades are quoted against, the main invoicing currency for commodities and a large share of cross-border trade, and the largest component of global central bank reserves. For a developer that has one practical consequence: when you need a rate between two other currencies, it is usually derived through the dollar. The fxapi USD exchange rate API reflects that – USD is the default base_currency, and you can switch to any other base when you need cross rates such as EUR/JPY (see base currency and cross rates).

USD facts for developers

• Where it’s used: the United States and its territories, plus several countries that use the dollar as their official currency, including Ecuador (since 2000), El Salvador (since 2001), Timor-Leste, the Marshall Islands, Micronesia and Palau. Panama uses it alongside the balboa (PAB), which is fixed at par.
• Symbol and formatting: $ before the amount, comma as thousands separator, period as decimal separator: $1,234.56. The $ sign is shared with CAD, AUD, MXN and many other dollars and pesos, so multi-currency UIs should show US$ or the ISO code.
• Minor unit: 2 decimals (cents).
• Central bank: the Federal Reserve System sets US monetary policy.
• Pegs to the dollar: several currencies are fixed or tightly managed against USD, including the HKD, AED and SAR. Their USD rates move very little; their rates against everything else move with the dollar.
• Events in the historical data: the dollar rose against most currencies in the second half of 2008 – the default sample date on this page, 2008-09-15, is the day Lehman Brothers filed for bankruptcy – and it rallied again during the March 2020 market sell-off.

Get USD rates with the fxapi API

/v1/latest and /v1/historical return rates per 1 USD on every plan, including Free. If you want converted amounts rather than unit rates, /v1/convert (Basic plan and up) multiplies for you and accepts an optional date. This Python snippet converts a USD invoice into four currencies today and at a past date:

import os
import requests

API = "https://api.fxapi.com/v1"
HEADERS = {"apikey": os.environ["FXAPI_KEY"]}

def convert_usd(amount, targets, date=None):
    params = {"base_currency": "USD", "currencies": ",".join(targets), "value": amount}
    if date:
        params["date"] = date
    r = requests.get(f"{API}/convert", params=params, headers=HEADERS, timeout=10)
    r.raise_for_status()
    return {code: item["value"] for code, item in r.json()["data"].items()}

print(convert_usd(2500, ["EUR", "GBP", "JPY", "MXN"]))
print(convert_usd(2500, ["EUR", "GBP"], date="2008-09-15"))

More Python patterns – retries, caching, pandas – are in the exchange rate API Python guide. Plan limits are on the pricing page.

Things to watch

• Don’t invert twice. Without base_currency, values are per 1 USD. If your code divides by the rate to get “USD per unit”, make sure no other layer does the same.
• Round late. Keep full precision while converting and round to the target currency’s minor unit only for display or settlement – JPY and KRW have 0 decimals, most others 2. See currency rounding and precision.
• Pegged pairs look flat. Don’t flag tiny USD/HKD or USD/SAR moves as anomalies; flag them if they leave the official band.

Popular USD pairs

Request any of these pairs – or any other combination of the 190+ supported currencies – with base_currency=USD:

Monthly averages and fluctuation for USD

# Monthly average USD rates for 2025 (IAS 21 / ASC 830)
curl -G "https://api.fxapi.com/v1/average" \
  -d date_from=2025-01-01 -d date_to=2025-12-31 -d period=month \
  -d base_currency=USD -d currencies=EUR,JPY,GBP \
  -H "apikey: $FXAPI_KEY"

# How did USD move over the last year?
curl -G "https://api.fxapi.com/v1/fluctuation" \
  -d date_from=2025-10-01 -d date_to=2026-10-01 \
  -d base_currency=USD -d currencies=EUR,JPY,GBP \
  -H "apikey: $FXAPI_KEY"

See the historical exchange rates API, average rates API and documentation for every parameter.

USD is one of 190+ currencies in fxapi, the FX rates API for developers – live rates, daily history since 1999 and monthly averages with one API key.

Frequently asked questions