Gamma near expiry
Last updated: May 30, 2026 · Options Greeks series
Gamma is the Greek that turns small moves into big problems near expiration. It's the rate of change of delta — how quickly your option's directional sensitivity shifts as the underlying moves. For long-dated options, gamma is small and gentle. For short-dated at-the-money options, gamma is enormous and unforgiving.
This is why every experienced options trader I know stays out of the last week before expiration on premium-selling positions. The math is just too unfavorable to short premium when gamma peaks.
What gamma actually measures
Gamma is the second derivative of option price with respect to underlying price. In plain English: it tells you how much delta changes when the underlying moves $1.
AAPL $195 call, 30 DTE, currently delta 0.30, gamma 0.05.
If AAPL rises $1: new delta = 0.30 + 0.05 = 0.35.
If AAPL rises $5: new delta = approximately 0.55.
For short premium sellers, gamma is the silent enemy. Your delta exposure shifts faster than you'd expect. A position that looked like “0.30 delta short” can become “0.70 delta short” in a single day if the underlying moves significantly.
Why gamma spikes near expiration
The intuition: at expiration, the option's payoff is either $0 (OTM) or stock price minus strike (ITM). At expiration delta is either exactly 0 or exactly 1.
Days before expiration, the option's delta has to converge from its current value (e.g., 0.30) to one of those two endpoints. The closer to expiration, the more rapidly delta has to swing as the underlying crosses the strike. That rate of change is gamma — and it peaks right at the strike just before expiration.
Visual: the gamma curve looks like a tall narrow peak at expiration, centered on the strike, with very little gamma far from the strike or far from expiration.
The 7-DTE ATM danger zone
Consider an AAPL $190 call with 7 days to expiration when AAPL is at $190 (perfectly ATM). Typical numbers:
- Delta: ~0.50
- Gamma: ~0.15
- Theta: -$0.25/day
If AAPL rises $3 in one day (1.6% move), the new delta is 0.50 + (3 × 0.15) = 0.95. Your option is now essentially long stock.
For a covered call seller, this means: you sold a call that was “30% probability of assignment” a few days ago. Now it's 95% certain to be assigned. You can either close at a big loss or accept the assignment that wasn't part of your original plan.
The 14-45 DTE income-seller sweet spot
Most experienced premium sellers stay in the 14-45 DTE window because it balances:
- Theta (good): Decay rate is meaningful — about 0.5-1% of option value per day.
- Gamma (bad, but tolerable): About 1/3 the gamma of a 7 DTE option at the same delta. Moves against you happen, but they don't blow through your strike instantly.
Below 14 DTE: theta is excellent but gamma is brutal. Single-day moves can blow up positions.
Above 45 DTE: gamma is gentle but theta is too slow. You're tying up capital for marginal decay.
The sweet spot: 21-35 DTE at 0.20-0.30 delta. That's the institutional buy-write standard for a reason — the gamma/theta trade-off is optimal.
Defensive moves when gamma risk peaks
If you have a position approaching expiration with strikes near the underlying:
1. Close at 50% profit. The standard rule. Once a short option has lost half its value, the remaining profit isn't worth the gamma exposure of holding longer.
2. Roll out 7-14 days before expiration. Even if the trade hasn't gone against you, rolling out captures the next cycle's theta while avoiding the gamma spike.
3. Avoid weekly options entirely. Some experienced traders just don't trade weekly options on individual names. The gamma risk is too high for the marginal premium gain.
4. Use spread strategies for very short-dated. If you must trade 7-DTE options, use vertical spreads instead of single-leg shorts. The long leg caps your gamma risk at the cost of some premium.
FAQ
Is gamma always negative for short options?
From the position's perspective, yes — short options have negative gamma exposure. You lose money faster as the stock moves in either direction. Long options have positive gamma.
Why is gamma highest at-the-money?
At-the-money is where delta is most uncertain (could swing from 0.5 to 0.95 or to 0.05 quickly). The further from ATM, the more committed delta already is, so it changes less.
Does gamma matter for 60+ DTE positions?
Less. Gamma decays as you move away from ATM and as time to expiration grows. A 60 DTE ATM option has roughly half the gamma of a 30 DTE ATM option. Long-dated positions are much more theta-driven than gamma-driven.
How can I monitor gamma in my account?
Most brokers display position-level Greeks including gamma. Aggregating across all positions gives you portfolio gamma. As a rule of thumb: total portfolio gamma above ~0.5 per $10k of capital is high and worth watching.
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