Currency Exchange Calculator
Calculate currency conversions with buy/sell rates and spread costs.
Find the true cost of exchanging money at banks, currency exchanges, and via card.
Currency exchange converts one currency to another using the prevailing exchange rate, minus any fees or spread charged by the conversion provider. Getting the best rate requires understanding how rates are quoted and what hidden fees look like.
Basic conversion formula: Amount in Target Currency = Amount in Source Currency × Exchange Rate
Inverse rate: If USD/EUR = 0.92 (1 USD buys 0.92 EUR), then EUR/USD = 1 ÷ 0.92 = 1.087 (1 EUR buys 1.087 USD)
Mid-market rate vs. retail rate: The mid-market rate (also called interbank rate) is the “true” exchange rate — the midpoint between buy and sell prices that banks use among themselves. Retail customers always receive a worse rate:
Effective Rate = Mid-Market Rate × (1 − Spread%)
Spread benchmarks by provider:
- Airport currency exchange kiosks: 7–15% spread (worst option)
- Bank branch: 3–8% spread
- Credit card foreign transaction: 1–3% (listed as “foreign transaction fee”)
- ATM abroad (using home debit card): 1–3% + ATM operator fee $3–$7
- Wise (TransferWise): 0.4–1.5% spread (excellent)
- Revolut / N26 (during market hours): near 0% spread, 0.5–2% on weekends
Total cost of exchange: Total Fee (%) = Spread% + Fixed Fee ÷ Amount Converted × 100
Fixed fee impact: A $5 fixed fee on a $50 exchange = 10% effective fee. On a $500 exchange = 1% effective fee. Always convert larger amounts at once when using fixed-fee services.
Dynamic Currency Conversion (DCC) — always decline: When abroad, merchants offer to charge your card in your home currency “for convenience.” This locks in an unfavorable rate (typically 5–8% worse). Always choose to pay in the local currency and let your card handle the conversion.
Worked example: Converting $1,000 USD to Euros for travel. Mid-market rate: 1 USD = 0.9200 EUR.
- Wise: Spread ~0.6% → effective rate: 0.9200 × (1 − 0.006) = 0.9145. Receive: 914.5 EUR. Fee: ~$6.
- Bank branch: Spread ~6% → effective rate: 0.9200 × 0.94 = 0.8648. Receive: 864.8 EUR. Fee: ~$49.70.
- Airport kiosk: Spread ~12% → effective rate: 0.9200 × 0.88 = 0.8096. Receive: 809.6 EUR. Fee: ~$104.
Using Wise vs. airport kiosk on a $1,000 conversion saves over $98 — enough for a hotel night in many European cities.