Slippage, Fees, and Funding: Why Your Crypto Backtest Lies (and How to Fix It)
Most crypto strategies fail live for one reason: costs. Learn how slippage, spreads, taker fees, and funding rates silently destroy backtests—and how to model them realistically.
Vantixs Team
Trading Education
Slippage, Fees, and Funding: Why Your Crypto Backtest Lies (and How to Fix It)
If your backtest looks amazing and your live results look “fine but worse”… you almost always have a cost-model problem.
Crypto is cost-heavy:
- wide spreads on alts
- taker fees when you cross the spread
- slippage during volatility
- funding for perpetuals
The 4 costs you must model
1) Fees (maker/taker)
Even “small” fees compound fast with high turnover.
2) Spread
Buying at ask and selling at bid is a cost. Many candle-based sims ignore it.
3) Slippage
Slippage is not constant. It spikes during breakouts and liquidation cascades.
4) Funding (perps)
Funding can flip the economics of a strategy that holds positions for days.
If you want realistic results, your backtest must include fees + spread + slippage (and funding for perps). If you can’t model them, assume worse and reduce position sizing.
Practical modeling (simple, workable)
- Fee: fixed maker/taker rate (start with taker)
- Spread: add a small penalty on entry/exit (bigger for alts)
- Slippage: base + volatility adjustment (worse in high ATR regimes)
- Funding: apply funding at funding intervals using historical funding data (or conservative estimate)
Next in the series
- Back to the hub: /blog/crypto-backtesting-complete-guide-2026
- Walk-forward: /blog/walk-forward-optimization-crypto
- Monte Carlo: /blog/monte-carlo-crypto-backtesting
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