Probability of Touch

Probability of touch (POT) measures the likelihood that a stock's price will reach a specific level at any point during the life of an option, not just at expiration. As a rule of thumb, the probability of touch is roughly double the probability of expiring in the money. If an option has a 20% chance of expiring ITM, there is roughly a 40% chance the stock will touch that strike at some point before expiration.

Why It Matters

Probability of touch is critical for traders who manage positions before expiration — which is most active options traders. While probability of profit tells you the odds at expiration, probability of touch tells you the odds of being tested along the way. A trade might have an 85% probability of profit at expiration, but a 30% probability of touch means there is a meaningful chance you will face an uncomfortable drawdown during the trade.

This distinction matters for risk management and position sizing. If you sell a put at a strike with a 40% probability of touch, you need to be prepared — financially and psychologically — for the stock to reach that level at some point. Knowing POT helps you set realistic expectations and avoid panic when positions are tested.

How It Works

The 2x rule: Probability of touch is approximately twice the probability of expiring ITM. This relationship comes from the mathematical properties of random walks. A stock that crosses a price level has roughly a 50% chance of finishing beyond it and a 50% chance of moving back — so if 20% of paths end ITM, roughly 40% of paths touch the strike along the way.

More precisely:

POT = approximately 2 x |Delta| of the option at that strike

A 25-delta put has roughly a 50% probability of touch. A 15-delta call has roughly a 30% probability of touch.

Factors that increase probability of touch:

• Higher implied volatility (wider expected range)
• More time to expiration (more opportunities for the stock to wander)
• Closer strikes (less distance for the stock to travel)

POT vs. probability of expiring ITM:

• POT is always higher than the probability of expiring ITM
• The ratio approaches 2x for OTM options and converges as options move ATM
• ATM options have a POT near 100% (the stock will almost certainly touch the current price again)

Using POT in trading:

• Position sizing: If POT is 50%, expect to manage or adjust roughly half the time
• Stop-loss placement: Set adjustment triggers at levels consistent with POT
• Strike selection: Selling at 15-delta (POT of 30%) means you will be tested in about 1 out of 3 trades
• Mental preparation: Knowing POT helps you distinguish between normal fluctuations and genuine threats to your position

Quick Example

You sell a 16-delta strangle on stock GHI — the short call is at $115 and the short put is at $85, with the stock at $100. Each side has roughly a 16% chance of expiring ITM.

Probability of touch for each side: approximately 32%. Probability that either side is touched: roughly 55% (since the events are not mutually exclusive but are partially correlated).

This means in more than half of all occurrences, the stock will touch one of your short strikes at some point before expiration — even though the trade has an estimated 70%+ probability of profit at expiration. Being prepared for this mid-trade stress is the difference between holding through to a profit and panic-closing for a loss.