Bid-Ask Spread Calculator
Compute spread, percent spread, and trade cost from bid/ask quotes. Panel remains open with zero defaults for quick checks.
Bid-ask spread is the difference between what buyers are willing to pay (bid) and what sellers are asking (ask). It’s a core measure of market liquidity and transaction cost. This calculator shows the spread in absolute and percentage terms and keeps the result panel open so you can see outputs even with zero inputs. Choose your currency for display, then enter bid and ask prices. If you also enter quantity, the calculator estimates total cost to lift the ask and total proceeds if you hit the bid, helping you see the slippage on a round trip.
Inputs: Bid price, Ask price, and optional Quantity. If bid or ask is zero, outputs stay at zero. Spread = Ask - Bid. Spread % = (Ask - Bid) / Ask. Mid price = (Bid + Ask) / 2. If you provide quantity, Total to Buy at Ask = Ask * Quantity; Total to Sell at Bid = Bid * Quantity; Round-trip Slippage = (Ask - Bid) * Quantity. These quick numbers help traders and analysts gauge execution cost.
Interpretation: Narrow spreads often mean deeper liquidity and lower cost to trade; wide spreads signal thin liquidity or higher uncertainty. For large orders, the quoted spread might understate real cost because price can move as you consume available depth. This calculator assumes you can transact the full quantity at the displayed bid/ask, which is a simplification.
Use cases: (1) Equities: compare spreads across tickers to decide which are cheap to trade. (2) FX: spreads vary by pair and session; small differences matter for frequent trading. (3) Crypto: spreads widen in volatile periods; a quick check can prevent costly market orders. (4) Options: wide spreads can dominate expected edge; know the spread before trading.
Risk notes: This tool ignores commissions, exchange fees, and slippage beyond the top-of-book. For more accuracy, consult your broker’s fee schedule and order book depth. Also, spreads can change rapidly; refresh quotes before trading.
Action steps: pick currency, enter bid and ask. If planning a trade, add quantity to see cost to buy and proceeds to sell. Use the percent spread to compare across instruments and to decide whether to place limit orders instead of market orders.
If the percent spread looks oddly large or negative, check that bid ≤ ask. If bid exceeds ask, the calculator still computes a negative spread to alert you to inconsistent data or crossed markets, which can occur briefly in fast conditions.
Remember: tight spreads are good, but size and depth matter too. Pair this quick spread check with volume and depth data when sizing trades.