Floating vs Fixed Rate — which to pick
Every modern crypto swap service offers two rate models. They look similar in the UI but behave very differently when prices move. Here is when each one makes sense, with concrete scenarios.
The problem both rate models solve
When you swap crypto-to-crypto through an aggregator (Changelly, ChangeNOW, SimpleSwap, FixedFloat, etc.), the price is set now but the actual swap happens later — after your deposit confirms on the source blockchain. That window can be seconds (Solana → Solana) or 30+ minutes (Bitcoin with low fees).
In that window, crypto markets move. Sometimes by 0.1%. Sometimes by 5%. So both you (the user) and the swap service (the liquidity provider) have to decide who absorbs that price movement.
Floating and fixed are the two answers to that question.
Floating rate — what really happens
With a floating rate, the price you see at the moment you start the swap is an estimate. The actual rate is determined when your deposit confirms.
Mechanics:
- You see an estimated rate (e.g. 1 BTC = 750 SOL).
- You send BTC. It takes ~15 minutes to confirm.
- When the deposit confirms, the swap engine looks at the live market price.
- You receive SOL at that rate, not the original estimate.
If SOL went down 2% during those 15 minutes, you actually receive a bit more SOL than the estimate (BTC bought more SOL). If SOL went up 2%, you receive a bit less. The risk is symmetric — markets can move either way.
The rate itself is also generally better than fixed by 0.3–1%, because the swap service isn't taking on any volatility risk and can offer tighter spreads.
Floating: better expected price, but ±1-3% uncertainty on the final amount. You're betting the market won't move much against you.
Fixed rate — what really happens
With fixed rate, the price you see is the price you get. The swap service guarantees the final amount, regardless of market movement during confirmation.
Mechanics:
- You see a fixed rate (e.g. 1 BTC = 745 SOL — note this is slightly worse than the floating estimate above).
- You get a deposit window — typically 15-20 minutes for fixed rate.
- You must deposit your BTC and have it confirm within that window.
- If you make the window, you receive exactly the SOL amount shown.
- If you miss the window, the swap automatically converts to floating rate.
The rate is worse by roughly 0.5–2% compared to floating. That difference is the swap service's premium for taking on the volatility risk during the deposit window. The longer/more volatile the chain, the bigger the premium.
Bitcoin → anything has the highest fixed-rate premium because Bitcoin confirmations are slow and the window for things to go wrong is largest. Solana → SPL token has almost no premium because confirmation is near-instant.
Concrete scenarios — what should I pick?
Scenario 1: Moving $10,000 worth of BTC to SOL for long-term holding
Pick floating. You don't care about a 1-2% short-term move because you're holding for months. The better expected price compounds.
Scenario 2: Swapping $500 of SOL to USDT to pay a bill in 30 minutes
Pick fixed. You know exactly how much USDT you need; you can't afford to come up short. Pay the 1% premium for certainty.
Scenario 3: Quick stablecoin shuffle — USDT-ERC20 to USDC-SPL
Either works. Stablecoins barely move; floating is fine. But the premium on fixed is also tiny (0.1-0.3%) because the underlying volatility is low. Coin flip.
Scenario 4: Sending Bitcoin from Coinbase to swap for ETH
Pick floating. Exchange withdrawal processing can take 10-60 minutes. If you pick fixed, you'll almost certainly miss the window and get auto-converted to floating anyway — at a worse rate than if you'd just picked floating to start with.
Scenario 5: Volatile market day (BTC moved 5% in the last hour)
Pick fixed. Volatile periods are precisely when fixed earns its premium. A 5% intraday move during your 15-minute window is no longer hypothetical.
Scenario 6: Tiny test swap ($10)
Either. Don't overthink small test transactions. Save the brainpower for the real swap that follows.
What happens if my deposit is late?
The key difference:
- Floating: nothing happens because there's no window. Whenever your deposit lands, it gets converted at the then-current rate.
- Fixed: if your deposit confirms after the window closes, the swap is automatically converted to floating rate. You're not refunded — you're just no longer guaranteed the rate you saw.
This is why the most expensive Bitcoin-side mistake is picking fixed with a low network fee. You think you're protecting yourself from volatility, but if your transaction is stuck in the mempool for 45 minutes, you end up with floating rate after the market has potentially moved against you.
If you're picking fixed rate, set your Bitcoin network fee to medium or high. Don't optimise for saving $2 in network fees and lose $50 in slippage.
TL;DR — the quick decision rule
If your deposit chain is fast (Solana, BNB, Polygon, most L2s) — floating is almost always right. The window is so short there's nothing to protect against, and you save the premium.
If your deposit chain is slow (Bitcoin, sometimes Ethereum during congestion) and you need a specific amount on the other side — fixed is right. Pay the premium for certainty.
If your deposit chain is slow and you're just moving funds around with no time pressure — floating wins on expected value. Markets are symmetric over many swaps; the lower fees compound.
Both options are available in seekerbridge on every swap. The toggle is right next to the rate, so you can decide swap by swap rather than setting a global default. Many people we've talked to default to floating for everything personal and switch to fixed only when the receiver is somebody else who's expecting an exact amount.