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Order Size Calculator
Before you spend a set budget on a coin, estimate roughly how much you'll get and how much the fee eats — so you have a number in mind before you head to the order page.
What this tool works out
The logic is simple: the nominal amount you can buy ≈ budget ÷ price; the fee is taken once out of the coin you receive at the rate you enter, so the amount you end up with = nominal amount × (1 − fee rate). Laying the numbers out lets you know, before you tap "Buy", roughly how much coin this money turns into and how much the fee bites — instead of ordering blind.
It doesn't go online or read your account; it just runs one bit of multiplication and division in your browser. It also won't decide for you whether to buy or how much is sensible — that's your call. It only helps you get the maths straight.
Worth a look while you're here
If you hit a "Buy button is greyed out" or a "minimum order size" message while ordering, it's usually not the tool getting the maths wrong — you've tripped a rule on the trading pair; see what to do when the buy button is greyed out. To work out which side of the pair is the quote currency, see which is which in a BTC/USDT pair.
Getting the most out of this tool
The formula: amount you can buy ≈ budget ÷ current price; the fee on this trade ≈ filled amount × fee rate (spot defaults to an estimate of 0.1%, and turning on BNB deductions or a higher VIP tier makes it lower). The coin you actually receive is a touch less than budget ÷ price, because the fee comes out of it.
Where it applies: it only gives you a rough pre-order estimate, an approximation for a market fill. If you place a limit order, the fill goes at the price you set; a market order can slip when the order book is thin, so the real amount will differ. Minimum order size and price precision follow the Binance trading page.
Common mistakes: (1) treating budget ÷ price as the exact amount you'll receive and ignoring the fee; (2) using the estimated amount straight as your order size, only to have it rejected for minimum order size or precision; (3) assuming the fee rate is fixed at 0.1%, when deductions and your tier can change it.
An example: with 500 USDT at a price of 50, you can roughly buy about 10 coins, the fee is about 0.5, and you actually receive about 9.99. To see how fees eat into profit, use it alongside the P&L / break-even calculator.