Slippage modeling
Options Slippage Modeling
Options slippage is not a small rounding detail. The spread is often the difference between a good-looking backtest and a tradable one.
Model options slippage from the bid/ask spread, contract multiplier, side, fill aggressiveness, and quote freshness. Treat midpoint fills as an assumption to validate, not a default truth.
Start with the quote
The bid and ask define the executable market. Midpoint is a useful reference, but a marketable buy pays closer to the ask and a marketable sell receives closer to the bid.
Scale by the multiplier
A 0.10 option price difference is $10 per contract before commissions. Multiply that across position size and every entry and exit in the backtest.
Use ranges, not one number
Compare midpoint, near-side, and marketable assumptions. If the strategy only survives the optimistic fill, the signal is probably not robust enough.
Quote vs Trade Timeline
Bid, ask, midpoint, and prints show why last price alone is fragile.
Bid/Ask Spread by Strike
Lower bars usually produce more defensible fill assumptions.
Related tools and docs
Backtest Realism Checker
Score contract, quote, trade, and spread assumptions before trusting a backtest.
Options Slippage Calculator
Translate bid/ask assumptions into dollar drag and breakeven movement.
Options Liquidity Scanner
Rank contracts by spread, volume, open interest, IV, and quote context.
Put/Call Ratio Dashboard
Track the current market put/call ratio beside weekly history across the last few years.
Options Chain Visualizer
Inspect heatmaps, IV smile, spread by strike, and volume versus open interest.
Options data API
See the full API surface behind these tools.
Historical options data API
Use contracts, quotes, trades, and aggregates for research workflows.
Options backtesting API
Plan historical contract and quote-aware fill sequences.