Theta Decay Calculator
See what time decay is worth to you per day.
Your numbers
The quoted option price, e.g. 3.00.
Calendar days, not trading days.
Defaults to one.
Per share per day, e.g. −0.05. Sign is ignored.
Results
- Average decay per day
- $10.00
- Decay at quoted theta
- $5.00
- Total premium collected
- $300.00
How it works
When you sell an option you are selling time, and theta measures how fast that time is worth less. Spreading the premium evenly across the days to expiration gives the average daily decay — the simplest useful figure, and the one that tells you what a day of patience is worth. Real decay is not even, though: it accelerates as expiration approaches, so a contract with 45 days left decays far more slowly today than it will in its final week. If your broker quotes theta, the second figure converts that per-share-per-day number into dollars for your actual position size, which is the more accurate reading for today specifically.
average decay per day = (premium × 100 × contracts) ÷ days to expiration · theta decay = |theta| × 100 × contracts
Worked example
One contract sold at 3.00 with 30 days left collects $300, so it averages $10 a day. If the broker quotes theta at −0.05, today's decay is closer to 0.05 × 100 = $5 — because decay accelerates later.
Common questions
Why do the two numbers disagree?
The average spreads decay evenly across the whole holding period; quoted theta is the rate right now. Early in the contract's life quoted theta is below average, and in the final week it is well above.
Does theta decay over weekends?
Yes. Time value erodes on calendar days, which is why option prices often gap down on Monday morning.
Is faster decay always better for a seller?
Faster decay means a shorter expiration, which also means less premium and less room to be wrong. Wheel sellers commonly settle between 30 and 45 days out as the compromise.
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- Covered Call Max Profit CalculatorWhat a covered call makes if the shares get called away.
- Options Liquidity CheckerCheck whether a contract is actually tradable before you sell it.
- Wheel Position Size CalculatorHow many contracts fit inside your risk budget.
- Wheel Expectancy CalculatorWhat one wheel cycle is worth on average, given your own numbers.
Stop doing this by hand
Wheel Income screens live option chains for cash-secured puts and covered calls, then tracks every cycle from assignment through called away.
Try the screenerFor information and educational purposes only. Not investment advice. Options carry risk, including loss of the entire position.