How Much Does Your Broker's FX Rate Really Cost You?
Buying an international stock means converting dollars into a foreign currency first, and most brokers don't charge a separate, visible fee for that conversion. Instead, they quote you a rate that's slightly worse than the true mid-market rate — the rate you'd see on a financial data site — and keep the gap as an implicit spread. Because it's baked into the rate rather than itemized as a fee, it's easy to miss. This calculator compares your broker's quoted rate to the mid-market rate to reveal that hidden cost in dollars.
How the Math Works
The spread percentage is the gap between the mid-market rate and your broker's quoted rate, divided by the mid-market rate. Multiplying your trade amount by that spread percentage gives you the hidden dollar cost — money you lose to the conversion before your order even reaches the foreign market. The same math applies whether you're converting dollars to buy or converting proceeds back after a sale.
You can find a currency's mid-market rate on most financial data sites or a currency converter, then compare it against the rate your brokerage actually applied to your trade confirmation. Spreads tend to be tighter on heavily traded currency pairs like the euro or yen and wider on less common ones. For investors who trade internationally often, even a spread under half a percent can add up to a meaningful cost over many trades, so it's worth checking periodically.
Frequently Asked Questions
Many quote a rate slightly worse than mid-market and keep the difference. It doesn't show as a line-item fee but is a real cost in the rate you get.
Roughly 0.03%-1% on major pairs, varying by broker and currency. Comparing the quoted rate to mid-market is the only reliable way to know your cost.
※ Actual spreads vary by broker, currency, and trade size; this is an estimate for reference only.