You check a rate Tuesday and it's different by Thursday. That's not instability — that's the foreign exchange market doing what it does every business second of the week: repricing the relative worth of 150-plus currencies in a market that turns over about $9.6 trillion a day. Understanding why rates move — and how far your bank's quote sits from the real one — is worth more than any timing trick.
Because almost nobody fixes them anymore. The major currencies — dollar, euro, yen, pound, and most others you'd recognize — float, meaning their price is set by supply and demand in continuous trading among banks, funds, companies, and governments. There's no single exchange with an opening bell; it's a decentralized dealer network, and the "rate" you see quoted is the market's rolling consensus. The Bank for International Settlements' triennial survey put daily turnover at $9.6 trillion in April 2025, up 28% from $7.5 trillion in 2022. At that volume, any persistent disagreement about a currency's value gets arbitraged away in milliseconds.
A minority of currencies don't float: the Hong Kong dollar trades in a tight band against the US dollar, and China manages the yuan within a controlled range. Even pegs move eventually, usually abruptly, when the central bank defending them runs out of reserves or patience. For the currencies most people convert, though, floating explains everything: no committee sets the euro-dollar rate; millions of trades do.
Six forces do most of the work. The currency converter page walks through each in depth; the short version:
Notice what's missing from that list: your vacation. Retail conversions are rounding errors here — the rate you get was set by institutions trading amounts with more digits than a mortgage.
The mid-market rate (also called the interbank or spot rate) is the midpoint between what dealers bid and ask in the wholesale market. It's the "honest" number — the one you see on this site, on Google, and in finance reporting. Retail providers quote you the mid-market rate minus a markup, called the spread, and that spread is where their profit lives. There's no cap on it — it's whatever the market, and your laziness, will bear.
How far below mid-market common channels typically land:
| Channel | Typical all-in cost vs mid-market | Notes |
|---|---|---|
| Specialist transfer apps | ~0.3-1.5% | Fee shown up front; closest most people get to wholesale |
| No-FX-fee credit or debit card | ~1-3% | Network processing plus any issuer margin; check the card's terms |
| Bank wire | Flat fee ($25-50) + ~1-3% | The flat fee dominates small transfers |
| Airport kiosk | ~6-15% | You're paying for the location, and they know it |
| "Pay in dollars" (DCC) | ~3-8% on top of the card's own cost | The merchant's terminal converts at a rate they set; decline it |
These are ranges, not quotes, but the shape of the table is stable year after year. To check any specific offer, divide the rate you're quoted by the mid-market rate: a quoted 0.90 against a mid-market 0.92 is a 2.2% haircut, not "basically the same." The percentage calculator handles the arithmetic if you'd rather not.
The percentages look small until you hold them against real amounts:
| Amount converted | 0.5% markup | 1% markup | 3% markup | 8% markup |
|---|---|---|---|---|
| $500 | $2.50 | $5 | $15 | $40 |
| $2,000 | $10 | $20 | $60 | $160 |
| $10,000 | $50 | $100 | $300 | $800 |
On a $2,000 trip fund, the difference between a specialist app and an airport kiosk is roughly $150 — a nice dinner, gone. On a $10,000 transfer (a tuition payment, a relocation, a property deposit), choosing the channel carefully is worth several hundred dollars for ten minutes of comparison.
The forex market closes around 5 p.m. Eastern on Friday and reopens around 5 p.m. Eastern on Sunday. During those roughly 48 hours, quoted rates freeze — the number on your converter is Friday's close wearing Monday's clothes. Two consequences: some card networks and transfer services add a weekend markup to cover the risk that the market gaps while shut, and Monday's first prices can jump past Friday's close if news broke. If a rate looks worse on a Saturday, that's often why. Crypto markets, by contrast, never close — the crypto converter runs on prices that trade straight through weekends and holidays.
None of this requires predicting currencies — which you can't, and neither can the people on television. The reliable moves are structural:
Live mid-market rates for 150+ currencies, updated hourly — measure every quote against it.
Currency Converter →Rates move because a $9.6-trillion-a-day market reprices them every second against interest rates, inflation, growth, politics, and flows. You can't outsmart that machine, and for everyday conversions you shouldn't try. What you can control is the gap between the mid-market rate and the rate you accept: decline DCC, avoid airport kiosks, and measure every offer against the real number before you commit. The spread is the only part of forex that's reliably negotiable — by walking away.
The forex market closes around 5 p.m. ET Friday and reopens around 5 p.m. ET Sunday, so quoted rates freeze over the weekend. Some card networks and transfer services add an extra weekend markup because they can't hedge in a closed market, and rates can gap when trading resumes Monday.
It depends which side of the trade you're on. A strong dollar helps Americans buying imports or traveling abroad and hurts US exporters, anyone earning foreign income, and unhedged US investors holding international assets. The reverse holds when the dollar weakens.
For most people, a specialist transfer service or a card with no foreign transaction fee, both typically landing within about 1-3% of the mid-market rate all-in. Airport kiosks are consistently the worst channel, often 6-15% below mid-market. Whatever the channel, compare the offered rate against a mid-market converter before committing.
No. The European Central Bank publishes reference rates that sit essentially at the mid-market level, and they are refreshed once per business day. Retail banks add a spread on top, commonly 0.5-5%, plus possible flat fees, so the rate you're actually quoted will be noticeably worse.