Theta
How much value you lose every single day
What is Theta?
Theta is rent. Every day you hold an option, you pay rent to the market. If the stock doesn't move enough to cover your rent, you lose money — even if you guessed the direction right.
Every option has two components of value: intrinsic value (how much it's in-the-money) and time value (the premium you pay for the possibility that things could still go your way before expiry). Theta measures how much that time value erodes each day. It's the silent cost of holding an option.
If theta is −0.08 on your option, you lose approximately $8 per contract per day — regardless of what the stock does. The stock can stay perfectly flat and you'll still be poorer tomorrow. Theta is the reason option buyers need the stock to move, and option sellers can profit just by waiting.
Theta represents the daily rent you pay to hold an option. Option buyers are tenants — they pay daily. Option sellers are landlords — they collect daily. The only way to stop paying rent is to sell the option or let it expire.
| Days to Expiry | Time Value Remaining | Daily Decay Rate | What's happening |
|---|---|---|---|
| 90 days | ~100% | Slow (~0.5%/day) | Plenty of time — decay is gentle |
| 60 days | ~82% | Moderate | Still manageable, but picking up |
| 30 days | ~58% | Faster (~1.5%/day) | Noticeable daily erosion |
| 14 days | ~39% | Fast (~2.5%/day) | Last two weeks — decay accelerates sharply |
| 7 days | ~27% | Very Fast (~4%/day) | The dangerous zone for option holders |
| 1 day | ~10% | Extreme | Almost all time value gone — intrinsic or nothing |
Theta decay is not linear — it follows a square root relationship with time. This means decay is slow early and accelerates exponentially in the final weeks before expiry. The last 30 days destroy far more time value than the first 60. This is sometimes called the "theta cliff."
Time Decay — Option Value Over Time
How to Read This Chart
- Left side = 90 days out. Time value is high, decay is slow. You're safe — for now.
- Right side = expiry day. Almost all time value is gone. Only intrinsic value remains.
- The curve is not straight. It's concave — the closer to expiry, the steeper the drop.
- The red shaded area represents value you've already lost. The steepest loss is in the final 30 days.
Frequently Asked
How do I know exactly how much theta costs me per day?
Look at your option's theta value on any broker platform. If theta = −0.06, you lose $6 per contract per day (theta × 100 shares). A theta of −0.20 costs $20/day. This number increases as expiry approaches for ATM options — it's not fixed.
Does theta decay happen on weekends when markets are closed?
Calendar time keeps moving even when markets don't. Typically, Friday's theta covers 3 calendar days — Friday, Saturday, Sunday. On Monday morning, your option opens reflecting 3 days of decay, not 1. This catches many beginners off guard after holding through a weekend.
Which options have the highest theta?
ATM options near expiry have the highest absolute theta. Time value peaks at ATM (deep ITM and far OTM options have less time value to lose). As you get closer to expiry, the daily decay of ATM options accelerates dramatically. Weekly options have the highest theta relative to their price.
Can I actually make money from theta?
Yes — and many professional traders do exactly this. Strategies like covered calls, cash-secured puts, iron condors, and credit spreads are all designed to collect theta. You sell options and hope they expire worthless. The tradeoff is you take on delta and gamma risk — if the stock makes a big move against you, theta gains are wiped out quickly.
If I buy an option and the stock moves in my favor, does theta still hurt me?
Yes, but delta gains can more than offset theta losses when the stock moves significantly. If you buy a 0.40 delta call and the stock rises $3, you gain ~$120 in delta while losing maybe $8–$15 to theta that day. The problem is when the stock barely moves — then theta erodes your premium steadily with nothing to offset it.
A Real Example
You buy 1 contract of a 45-day SPY ATM call for $8.00. Theta = −0.10. SPY stays flat.
Option worth ≈ $7.90. Theta took −$10 overnight while you weren't watching.
By Monday open: worth ≈ $7.60. You paid −$30 for three days of calendar time, with the market closed two of them.
Now at 15 DTE, theta has accelerated. Option worth ≈ $3.50. You've lost $450 — over half your premium — with SPY doing nothing.
This is the most common way retail traders lose money: buying options and hoping. The clock is always running. You need SPY to move enough, fast enough, to outrun daily theta. When it doesn't, theta wins.
What Beginners Get Wrong
Quick Quiz
Answer all questions and check your score.
1 An option has theta of −0.05. How much value does one contract lose per day (all else equal)?
2 Theta decay accelerates most sharply:
3 Who profits from theta decay?
4 You buy an ATM call for $3.00 with theta = −0.10. After 5 days (nothing else changes), the option is worth approximately:
5 Which option typically has the highest absolute theta?