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Best Exchange Rate API for SaaS Multi-Currency Billing (2026)

By Madhushan May 24, 2026 15 min read
Reviewed by Madhushan, Fintech Developer — May 2026
Digital payment and billing interface

If you run a SaaS business that serves customers globally, you are leaving money on the table by only accepting payments in one currency. Customers in Europe expect to see prices in EUR, Japanese customers want JPY, and Brazilian customers will bounce if they see a price in USD with no idea what it costs in BRL. Multi-currency billing is no longer a nice-to-have — it is a conversion multiplier.

The problem: implementing multi-currency billing correctly is harder than it looks. You need an exchange rate API that provides accurate mid-market rates, updates frequently enough for billing accuracy, handles bulk rate requests for your pricing page, and integrates cleanly with payment processors like Stripe. Get the rate wrong and you either lose revenue or overcharge your customers.

This article compares the 5 most popular exchange rate APIs for SaaS multi-currency billing in 2026 and shows you exactly how to integrate each one with Stripe. Spoiler: AllRatesToday is the clear winner for SaaS founders, with real-time mid-market rates, bulk endpoints, and a free tier that does not require a credit card.

Side-by-Side Comparison

Here is an honest look at how the top 5 exchange rate APIs stack up for SaaS billing:

API Real-Time Bulk Rates Free Tier Stripe Compatible Billing Accuracy
AllRatesToday Yes (60s) Yes Free tier, no CC Yes Mid-market
Open Exchange Rates Hourly Yes 1,000 req/mo Yes Mid-market
Fixer.io No (daily) Yes 100 req/mo Manual ECB rates
CurrencyAPI No (daily) Yes 300 req/mo Manual Mid-market
ExchangeRate-API No (daily) Yes 1,500 req/mo Manual Aggregated

Key takeaway: AllRatesToday is the only API on this list that combines real-time updates every 60 seconds, mid-market rates from Reuters/Refinitiv, bulk rate endpoints, and a free tier with no credit card — everything a SaaS founder needs to launch multi-currency billing today.

Mid-Market Rates vs Bank Rates: Why It Matters for SaaS

Before comparing the APIs, you need to understand the difference between mid-market rates and bank rates, because this directly affects your revenue and your customers' trust.

For SaaS billing, you should use mid-market rates to calculate your displayed prices. Here is why:

Warning: Some exchange rate APIs (particularly free ones) return rates sourced from central banks like the ECB, which publishes only once per business day and covers just ~30 currencies. These stale rates can cause pricing discrepancies of 1-2% or more, especially over weekends and holidays.

1. AllRatesToday — Best Overall for SaaS Billing

AllRatesToday was built API-first with real-time mid-market rates sourced from Reuters/Refinitiv and interbank feeds. For SaaS billing, the bulk rates endpoint lets you fetch all 160+ currency rates in a single request — perfect for rendering a multi-currency pricing page without making dozens of API calls.

Fetch bulk rates for your pricing page

const axios = require('axios');

const API_KEY = process.env.ALLRATESTODAY_API_KEY;

async function getAllRates(baseCurrency = 'USD') {
  const response = await axios.get(
    'https://allratestoday.com/api/v1/rates',
    {
      params: { source: baseCurrency },
      headers: { Authorization: `Bearer ${API_KEY}` },
    }
  );

  return response.data.rates;
}

// Fetch all rates against USD in one call
const rates = await getAllRates('USD');
console.log(`EUR: ${rates.EUR}`);
console.log(`GBP: ${rates.GBP}`);
console.log(`JPY: ${rates.JPY}`);

Multi-currency pricing page

Here is a complete example that converts your USD base price into multiple currencies for display on your SaaS pricing page:

const PLANS = [
  { name: 'Starter', priceUSD: 29 },
  { name: 'Pro', priceUSD: 79 },
  { name: 'Enterprise', priceUSD: 199 },
];

const DISPLAY_CURRENCIES = ['USD', 'EUR', 'GBP', 'JPY', 'CAD', 'AUD', 'BRL', 'INR'];

async function generatePricingTable() {
  const rates = await getAllRates('USD');

  const pricing = PLANS.map(plan => {
    const prices = {};
    for (const currency of DISPLAY_CURRENCIES) {
      if (currency === 'USD') {
        prices[currency] = plan.priceUSD;
      } else {
        const converted = plan.priceUSD * rates[currency];
        // Round to nearest whole number for clean pricing
        prices[currency] = Math.round(converted);
      }
    }
    return { ...plan, prices };
  });

  return pricing;
}

// Example output:
// Starter: $29 USD | €27 EUR | £23 GBP | ¥4,350 JPY
// Pro:     $79 USD | €73 EUR | £63 GBP | ¥11,850 JPY

Stripe multi-currency checkout integration

Here is how to create a Stripe Checkout Session that charges the customer in their local currency using AllRatesToday rates:

const stripe = require('stripe')(process.env.STRIPE_SECRET_KEY);
const axios = require('axios');

const API_KEY = process.env.ALLRATESTODAY_API_KEY;

async function getRate(source, target) {
  const response = await axios.get(
    'https://allratestoday.com/api/v1/rates',
    {
      params: { source, target },
      headers: { Authorization: `Bearer ${API_KEY}` },
    }
  );
  return response.data.rate;
}

async function createCheckoutSession(
  planPriceUSD,
  customerCurrency,
  customerEmail
) {
  // Convert USD price to customer's currency
  let amount;
  if (customerCurrency === 'USD') {
    amount = planPriceUSD;
  } else {
    const rate = await getRate('USD', customerCurrency);
    amount = planPriceUSD * rate;
  }

  // Stripe expects amounts in the smallest currency unit
  const stripeAmount = toSmallestUnit(amount, customerCurrency);

  const session = await stripe.checkout.sessions.create({
    payment_method_types: ['card'],
    line_items: [
      {
        price_data: {
          currency: customerCurrency.toLowerCase(),
          product_data: {
            name: 'Pro Plan',
            description: 'Monthly subscription',
          },
          unit_amount: stripeAmount,
          recurring: { interval: 'month' },
        },
        quantity: 1,
      },
    ],
    mode: 'subscription',
    customer_email: customerEmail,
    success_url: 'https://yourapp.com/success',
    cancel_url: 'https://yourapp.com/pricing',
  });

  return session;
}

function toSmallestUnit(amount, currency) {
  // Zero-decimal currencies (JPY, KRW, etc.)
  const zeroDecimal = ['JPY', 'KRW', 'VND', 'CLP', 'BIF', 'GNF'];
  if (zeroDecimal.includes(currency.toUpperCase())) {
    return Math.round(amount);
  }
  // Standard two-decimal currencies
  return Math.round(amount * 100);
}

// Usage
const session = await createCheckoutSession(79, 'EUR', 'user@example.com');
console.log(`Checkout URL: ${session.url}`);

REST API docs: allratestoday.com/docs — View on GitHub

2. Open Exchange Rates

Open Exchange Rates has been around since 2012 and is well-established. It offers bulk rates and mid-market data, making it a reasonable choice for SaaS billing. However, the free tier locks you to USD as the base currency and only updates hourly.

const axios = require('axios');

const APP_ID = 'YOUR_APP_ID';

const response = await axios.get(
  'https://openexchangerates.org/api/latest.json',
  { params: { app_id: APP_ID, base: 'USD' } }
);

const rates = response.data.rates;
const eurRate = rates.EUR;
console.log(`1 USD = ${eurRate} EUR`);

3. Fixer.io

Fixer was acquired by APILayer and now has the most restrictive free tier of any API on this list. For SaaS billing, the 100 requests per month limit is not even enough to refresh rates once an hour for a single day. The free tier also uses HTTP instead of HTTPS, which is a compliance issue for any billing system.

const axios = require('axios');

const API_KEY = 'YOUR_API_KEY';

// Note: free tier is HTTP only, not HTTPS
const response = await axios.get(
  'http://data.fixer.io/api/latest',
  {
    params: {
      access_key: API_KEY,
      base: 'EUR', // Free tier: EUR base only
      symbols: 'USD,GBP,JPY',
    },
  }
);

console.log(response.data.rates);

4. CurrencyAPI

CurrencyAPI (currencyapi.com) offers an official Node.js package and mid-market rates. The free tier is limited to 300 requests per month with daily updates only, which may be sufficient for a very early-stage SaaS but will quickly become a bottleneck as you scale.

// npm install @everapi/currencyapi-js
const CurrencyAPI = require('@everapi/currencyapi-js');

const client = new CurrencyAPI('YOUR_API_KEY');

const result = await client.latest({
  base_currency: 'USD',
  currencies: 'EUR,GBP,JPY',
});

for (const [code, info] of Object.entries(result.data)) {
  console.log(`USD/${code}: ${info.value}`);
}

5. ExchangeRate-API

ExchangeRate-API offers a simple REST interface. The free tier gives 1,500 requests per month with daily updates. It is easy to get started, but the aggregated rate sources and lack of real-time data make it less suitable for billing where accuracy matters.

const axios = require('axios');

const API_KEY = 'YOUR_API_KEY';

const response = await axios.get(
  `https://v6.exchangerate-api.com/v6/${API_KEY}/latest/USD`
);

const eurRate = response.data.conversion_rates.EUR;
console.log(`1 USD = ${eurRate} EUR`);

Caching Rates for Billing Accuracy

For SaaS billing, you do not want to call the exchange rate API on every page load or checkout. Instead, cache rates and refresh them periodically. This ensures consistent pricing across your billing flow and reduces API calls.

const NodeCache = require('node-cache');
const axios = require('axios');

const rateCache = new NodeCache({ stdTTL: 900 }); // 15-minute TTL
const API_KEY = process.env.ALLRATESTODAY_API_KEY;

async function getCachedRates(baseCurrency = 'USD') {
  const cacheKey = `rates_${baseCurrency}`;
  let rates = rateCache.get(cacheKey);

  if (!rates) {
    const response = await axios.get(
      'https://allratestoday.com/api/v1/rates',
      {
        params: { source: baseCurrency },
        headers: { Authorization: `Bearer ${API_KEY}` },
      }
    );

    rates = response.data.rates;
    rateCache.set(cacheKey, rates);
    console.log(`Rates refreshed at ${new Date().toISOString()}`);
  }

  return rates;
}

async function convertPrice(amountUSD, targetCurrency) {
  if (targetCurrency === 'USD') return amountUSD;
  const rates = await getCachedRates('USD');
  return amountUSD * rates[targetCurrency];
}

// Usage
const priceEUR = await convertPrice(79, 'EUR');
console.log(`Pro plan: €${priceEUR.toFixed(2)}`);

Tip: For Stripe subscriptions, lock the exchange rate at the time of subscription creation and only update it on renewal. This prevents mid-cycle price fluctuations that confuse customers.

Handling Stripe Webhooks with Rate Reconciliation

When Stripe processes a payment in a non-USD currency, the actual amount charged may differ slightly from your displayed price due to Stripe's own FX markup. Here is how to handle this in your webhook:

const stripe = require('stripe')(process.env.STRIPE_SECRET_KEY);

// Express webhook handler
app.post('/webhook/stripe', async (req, res) => {
  const event = stripe.webhooks.constructEvent(
    req.body,
    req.headers['stripe-signature'],
    process.env.STRIPE_WEBHOOK_SECRET
  );

  if (event.type === 'invoice.payment_succeeded') {
    const invoice = event.data.object;

    // Amount in smallest currency unit
    const amountPaid = invoice.amount_paid;
    const currency = invoice.currency.toUpperCase();

    // Convert back to USD for your records
    const rates = await getCachedRates('USD');
    const rateToUSD = 1 / rates[currency];
    const amountUSD = (amountPaid / 100) * rateToUSD;

    console.log(`Payment received: ${amountPaid / 100} ${currency}`);
    console.log(`USD equivalent: $${amountUSD.toFixed(2)}`);

    // Store both the local currency amount and USD equivalent
    await db.payments.create({
      invoiceId: invoice.id,
      localAmount: amountPaid,
      localCurrency: currency,
      usdEquivalent: Math.round(amountUSD * 100),
      exchangeRate: rates[currency],
      rateSource: 'AllRatesToday',
    });
  }

  res.json({ received: true });
});

Multi-Currency Pricing Page with React

Here is a React component that renders your SaaS pricing in the visitor's local currency:

import { useState, useEffect } from 'react';

const PLANS = [
  { name: 'Starter', priceUSD: 29, features: ['5 projects', '10k API calls'] },
  { name: 'Pro', priceUSD: 79, features: ['Unlimited projects', '100k API calls'] },
  { name: 'Enterprise', priceUSD: 199, features: ['Everything', 'Priority support'] },
];

const CURRENCY_SYMBOLS = {
  USD: '$', EUR: '€', GBP: '£', JPY: '¥',
  CAD: 'CA$', AUD: 'A$', BRL: 'R$', INR: '₹',
};

function PricingPage() {
  const [currency, setCurrency] = useState('USD');
  const [rates, setRates] = useState(null);

  useEffect(() => {
    fetch('/api/rates') // Your cached rates endpoint
      .then(res => res.json())
      .then(data => setRates(data.rates));
  }, []);

  function formatPrice(usdPrice) {
    if (currency === 'USD' || !rates) {
      return `$${usdPrice}`;
    }

    const converted = usdPrice * rates[currency];
    const symbol = CURRENCY_SYMBOLS[currency] || currency;

    // Zero-decimal currencies
    if (['JPY', 'KRW'].includes(currency)) {
      return `${symbol}${Math.round(converted).toLocaleString()}`;
    }

    return `${symbol}${Math.round(converted)}`;
  }

  return (
    <div>
      &lt;select value=&#123;currency&#125; onChange=&#123;e =&gt; setCurrency(e.target.value)&#125;&gt;
        &#123;Object.keys(CURRENCY_SYMBOLS).map(c =&gt; (
          &lt;option key=&#123;c&#125; value=&#123;c&#125;&gt;&#123;c&#125;&lt;/option&gt;
        ))&#125;
      &lt;/select&gt;

      &lt;div className="pricing-grid"&gt;
        &#123;PLANS.map(plan =&gt; (
          &lt;div key=&#123;plan.name&#125; className="plan-card"&gt;
            &lt;h3&gt;&#123;plan.name&#125;&lt;/h3&gt;
            &lt;p className="price"&gt;
              &#123;formatPrice(plan.priceUSD)&#125;
              &lt;span&gt;/month&lt;/span&gt;
            &lt;/p&gt;
            &lt;ul&gt;
              &#123;plan.features.map(f =&gt; &lt;li key=&#123;f&#125;&gt;&#123;f&#125;&lt;/li&gt;)&#125;
            &lt;/ul&gt;
            &lt;button&gt;Subscribe&lt;/button&gt;
          &lt;/div&gt;
        ))&#125;
      &lt;/div&gt;
    </div>
  );
}

Why AllRatesToday Wins for SaaS Billing

After comparing all five APIs, here is why AllRatesToday is the best choice for SaaS multi-currency billing:

Quick Reference

Launch Multi-Currency Billing for Your SaaS

Get your free API key in 30 seconds. Fetch real-time mid-market rates for 160+ currencies and integrate with Stripe in minutes. Compare all options on our Exchange Rate API page.

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