Bank of Mongolia Exchange Rate API: Official MNT Rates as JSON

The Bank of Mongolia publishes the official exchange rates that accounting, tax, and customs rules in Mongolia reference — published official rates, not moving market prices. This guide shows how to pull them as JSON: via a REST endpoint or the zero-dependency bank-of-mongolia-exchange-rate npm package.

What the BOM publishes

• ~38 currencies against the tögrög — from USD and CNY (the trade anchors) to the full official table.
• The bank's own publication date on every response, so a rate is always citable.
• No gaps to trip over — weekends and Mongolian holidays resolve to the most recent published rates and are flagged explicitly.

The USD/MNT and CNY/MNT rates anchor the table — Mongolia's mining exports and Chinese trade both settle around the Bank of Mongolia's official print, the legal reference for customs and tax.

Why official rates, not market rates

A live mid-market feed answers "what is USD/MNT trading at right now?" — the right tool for checkouts and dashboards. But accountants, auditors, and tax authorities ask a different question: "which rate were you required to use for this date?" That answer comes from the Bank of Mongolia's published rates, and it never changes after publication.

Get the latest rates (REST)

curl "https://allratestoday.com/api/v1/central-bank/bom/latest" \
  -H "Authorization: Bearer YOUR_API_KEY"

The response is the bank's most recent published data — every rate and the publication date. The latest rates are available on every plan, including the free tier (300 requests/month, no credit card).

The npm SDK

npm install bank-of-mongolia-exchange-rate

import { getRate, getLatestRates } from 'bank-of-mongolia-exchange-rate';

// One pair at the official BOM rate
const pair = await getRate('USD', 'MNT', { apiKey: 'art_live_...' });
console.log(pair.rate, pair.rate_date);

// The bank's full published table
const table = await getLatestRates({ apiKey: 'art_live_...' });
console.log(table.rate_date, table.rates.length);

Zero dependencies, TypeScript types included, and it runs anywhere fetch exists — Node 18+, Bun, Deno, and edge runtimes.

Historical rates for an invoice date

import { getRatesForDate, getHistory } from 'bank-of-mongolia-exchange-rate';

// The official rates for an invoice date — non-publication days return
// the most recent published date, flagged via published_on_requested_date.
const day = await getRatesForDate('2026-06-30', { apiKey: 'art_live_...' });

// Time series for one pair
const series = await getHistory(
  { source: 'USD', target: 'MNT', from: '2026-01-01' },
  { apiKey: 'art_live_...' }
);

Historical dates and time series need a paid plan; the latest rates stay free.

Published vs derived pairs

If the BOM does not print a pair directly, the API resolves it from the bank's published rates — an inverse, or a cross rate via MNT — and flags it derived: true with the method used. Official and computed values are never silently mixed, which is exactly the distinction an auditor will ask about.

A series that grows every day

AllRatesToday began archiving the Bank of Mongolia table in August 2026, and every banking day adds another citable print. The latest table is always one free API call away, and the archive deepens daily.

FAQ

Does the Bank of Mongolia have an official exchange rate API?

The BOM publishes its official rates on its own site, and AllRatesToday serves the same published rates as clean JSON via REST or the bank-of-mongolia-exchange-rate npm package. The latest table is free.

How often do Bank of Mongolia rates update?

Every banking day, Ulaanbaatar time. These are published official rates, not moving market prices — every API response carries the publication date so you can cite it.

Can I get the BOM rate for a past date, like an invoice date?

Yes. The /central-bank/bom/rates-for-date endpoint returns the official rates for any archived date. Non-publication days resolve to the most recent published date and are flagged, so your audit trail stays honest. Historical dates require a paid plan; latest rates are free.