Simple Currency Converter

How Currency Conversion Works

Currency conversion multiplies an amount in one currency by the current exchange rate to get the equivalent in another currency. The complexity lies in understanding which rate applies and what fees are hidden in it.

Basic conversion formula:

Amount in Target Currency = Amount in Source Currency × Exchange Rate

Worked example:

Converting $1,000 USD to Euros at a rate of 0.92 EUR/USD:

€1,000 × 0.92 = €920

Converting €920 back to USD at 1.087 USD/EUR:

€920 × 1.087 = $1,000 (round trip, no fees)

Bid-ask spread:

Banks and exchanges profit from the spread between buying and selling rates:

• Mid-market rate (the “real” rate): 1.087 USD/EUR
• Bank selling rate (what you pay to buy EUR): 1.045
• Bank buying rate (what you receive selling EUR): 1.130

The spread is the hidden fee. On $1,000, a 3% spread costs you $30.

Cross-rate calculation:

To convert between two currencies that don’t have a direct quote (e.g., BRL to JPY):

BRL/JPY = BRL/USD × USD/JPY

If 1 USD = 4.97 BRL and 1 USD = 149 JPY:

1 BRL = 149 ÷ 4.97 = 29.98 JPY

Best practices to minimize fees:

• Use Wise (formerly TransferWise) or Revolut — both offer mid-market rates with small fixed fees
• Avoid airport exchange booths — spreads of 8–15% are common
• When abroad, choose to pay in local currency (not your home currency) — dynamic currency conversion (DCC) charges 3–7% extra
• Credit cards with no foreign transaction fees (Chase Sapphire, Capital One Venture) typically offer near-mid-market rates