Build a Currency Converter

This guide shows how to fetch live NGN exchange rates and build a bidirectional currency converter, the same feature NGN Market uses on its forex page. Users can type an amount in NGN and see the equivalent in USD, GBP, EUR, and more, or convert the other way around. Endpoint used:

GET /forex/current (Free plan): all current NGN rates in one call

How the rates work

Each rate is how many naira one unit of the foreign currency buys, and inverse_rate is the reverse. For example:

{ "currency": "USD", "rate": 1603.50, "inverse_rate": 0.000624 }

This means $1 = ₦1,603.50, so to convert:

USD → NGN: amount_usd × rate
NGN → USD: amount_ngn ÷ rate (or amount_ngn × inverse_rate)

Step 1: Fetch all rates

One call returns every supported currency pair.

curl https://api.ngnmarket.com/v1/forex/current \
  -H "Authorization: Bearer ngm_live_YOUR_KEY"

const API_KEY = 'ngm_live_YOUR_KEY';

async function fetchRates() {
  const res = await fetch('https://api.ngnmarket.com/v1/forex/current', {
    headers: { Authorization: `Bearer ${API_KEY}` },
  });
  const { data } = await res.json();

  // Build a currency code → rate map (naira per unit of each currency)
  return Object.fromEntries(data.rates.map(r => [r.currency, r.rate]));
}

import requests

API_KEY = 'ngm_live_YOUR_KEY'

def fetch_rates():
    res = requests.get(
        'https://api.ngnmarket.com/v1/forex/current',
        headers={'Authorization': f'Bearer {API_KEY}'},
    )
    rates = res.json()['data']['rates']
    return {r['currency']: r['rate'] for r in rates}

Sample response (trimmed)

{
  "success": true,
  "data": {
    "target": "NGN",
    "date": "2026-04-21",
    "rates": [
      { "currency": "USD", "rate": 1603.50, "inverse_rate": 0.000624, "daily_change": 2.5,  "daily_change_percent": 0.1561, "last_updated": "2026-04-21" },
      { "currency": "GBP", "rate": 2037.80, "inverse_rate": 0.000491, "daily_change": 0,    "daily_change_percent": 0,      "last_updated": "2026-04-21" },
      { "currency": "EUR", "rate": 1748.20, "inverse_rate": 0.000572, "daily_change": -5.1, "daily_change_percent": -0.2909, "last_updated": "2026-04-21" }
    ]
  }
}

Step 2: Conversion logic

function convert({ amount, from, to, rates }) {
  // rates[code] = naira per 1 unit of that currency
  if (from === 'NGN') {
    // NGN → foreign
    return amount / rates[to];
  } else if (to === 'NGN') {
    // foreign → NGN
    return amount * rates[from];
  } else {
    // foreign → foreign (route through NGN)
    const inNgn = amount * rates[from];
    return inNgn / rates[to];
  }
}

// Examples
const rates = await fetchRates();
console.log(convert({ amount: 100000, from: 'NGN', to: 'USD', rates })); // ₦100,000 → USD
console.log(convert({ amount: 500,    from: 'USD', to: 'NGN', rates })); // $500 → NGN
console.log(convert({ amount: 200,    from: 'USD', to: 'GBP', rates })); // $200 → GBP

def convert(amount, from_currency, to_currency, rates):
    # rates[code] = naira per 1 unit of that currency
    if from_currency == 'NGN':
        return amount / rates[to_currency]
    elif to_currency == 'NGN':
        return amount * rates[from_currency]
    else:
        # route through NGN
        in_ngn = amount * rates[from_currency]
        return in_ngn / rates[to_currency]

rates = fetch_rates()
print(convert(100_000, 'NGN', 'USD', rates))  # ₦100,000 → USD
print(convert(500,     'USD', 'NGN', rates))  # $500 → NGN
print(convert(200,     'USD', 'GBP', rates))  # $200 → GBP

React component (bidirectional)

Typing in either input updates the other in real time.

React

import { useEffect, useState } from 'react';

const API_KEY    = 'ngm_live_YOUR_KEY';
const CURRENCIES = ['USD', 'GBP', 'EUR', 'CAD', 'CNY', 'AED'];

async function fetchRates() {
  const res = await fetch('https://api.ngnmarket.com/v1/forex/current', {
    headers: { Authorization: `Bearer ${API_KEY}` },
  });
  const { data } = await res.json();
  return Object.fromEntries(data.rates.map(r => [r.currency, r.rate]));
}

export function CurrencyConverter() {
  const [rates,      setRates]     = useState({});
  const [currency,   setCurrency]  = useState('USD');
  const [ngnAmount,  setNgnAmount] = useState('');
  const [fxAmount,   setFxAmount]  = useState('');

  useEffect(() => { fetchRates().then(setRates); }, []);

  const rate = rates[currency];

  function handleNgnChange(val) {
    setNgnAmount(val);
    setFxAmount(rate && val ? (parseFloat(val) / rate).toFixed(4) : '');
  }

  function handleFxChange(val) {
    setFxAmount(val);
    setNgnAmount(rate && val ? (parseFloat(val) * rate).toFixed(2) : '');
  }

  return (
    <div>
      <label>
        NGN (₦)
        <input
          type="number"
          value={ngnAmount}
          onChange={e => handleNgnChange(e.target.value)}
          placeholder="0.00"
        />
      </label>

      <select value={currency} onChange={e => { setCurrency(e.target.value); setFxAmount(''); }}>
        {CURRENCIES.map(c => <option key={c} value={c}>{c}</option>)}
      </select>

      <label>
        {currency}
        <input
          type="number"
          value={fxAmount}
          onChange={e => handleFxChange(e.target.value)}
          placeholder="0.00"
        />
      </label>

      {rate && (
        <p>1 {currency} = ₦{rate.toLocaleString(undefined, { maximumFractionDigits: 2 })}</p>
      )}
    </div>
  );
}

Vanilla JavaScript (with a rate table)

Display all rates alongside the converter:

JavaScript

const API_KEY    = 'ngm_live_YOUR_KEY';
const CURRENCIES = ['USD', 'GBP', 'EUR', 'CAD', 'CNY', 'AED'];

async function init() {
  const res    = await fetch('https://api.ngnmarket.com/v1/forex/current', {
    headers: { Authorization: `Bearer ${API_KEY}` },
  });
  const { data } = await res.json();
  const rates  = Object.fromEntries(data.rates.map(r => [r.currency, r.rate]));

  // Render rates table
  const tbody = document.querySelector('#rates-table tbody');
  data.rates.forEach(({ currency, rate, inverse_rate }) => {
    const row = tbody.insertRow();
    row.innerHTML = `
      <td>${currency}</td>
      <td>${rate.toLocaleString(undefined, { maximumFractionDigits: 2 })}</td>
      <td>${inverse_rate.toFixed(6)}</td>
    `;
  });

  // Wire up converter inputs
  const ngnInput = document.getElementById('ngn-input');
  const fxInput  = document.getElementById('fx-input');
  const fxSelect = document.getElementById('fx-select');

  ngnInput.addEventListener('input', () => {
    const rate = rates[fxSelect.value];
    fxInput.value = rate ? (parseFloat(ngnInput.value) / rate).toFixed(4) : '';
  });

  fxInput.addEventListener('input', () => {
    const rate = rates[fxSelect.value];
    ngnInput.value = rate ? (parseFloat(fxInput.value) * rate).toFixed(2) : '';
  });
}

init();

Tips

Cache rates for the session. Forex rates update daily, so one fetch per page load is sufficient. No need to poll on an interval like equity prices. Always show the rate date. The response includes a date (and a last_updated per currency). Display it near your rates so users know how fresh the data is. Cross-pair conversion routes through NGN. All rates are naira per unit, so to convert USD → GBP you multiply by the USD rate to get naira, then divide by the GBP rate. The convert() function above handles this automatically.

Forex current reference

Full response spec for GET /forex/current

Forex history reference

Historical NGN rates with date range filtering

​How the rates work

​Step 1: Fetch all rates

​Sample response (trimmed)

​Step 2: Conversion logic

​React component (bidirectional)

​Vanilla JavaScript (with a rate table)

​Tips