TRIED & TRADED
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What is the 21-DTE exit?

  • The 21-DTE exit closes the trade when three weeks are left, in profit or not.
  • It is the most repeated exit rule in retail options trading, and it is not really a rule about time.

What it is

  • Open the trade around 45 days out. That is the tenor the rule grew up alongside.
  • Close it at 21 days, whatever it is worth.
  • Usually paired with a profit target, so most positions never reach the date.
  • The date is checked, not negotiated. That is what separates it from “closing early when it feels right”.

Where it came from

  • It came out of published research from the tastytrade side of the retail options world, on managing short-premium trades rather than holding them out.
  • It spread from there into podcasts, courses and broker education until it stopped being attributed to anyone.
  • We have not reproduced their numbers, and this page doesn’t repeat them as if we had.
  • What we can say is what the rule is managing, because that part is arithmetic.

What it is actually managing

Take the specification this site uses for the bull put spread and let it reach the strike it sold. Nothing about the position changes. Only the calendar moves.

Days leftGammaTheta a day
45−1.18$0.67
21−2.90$1.94
7−9.25$6.81
  • The income rises. Theta goes from 67 cents a day to $6.81.
  • So does the speed you can be hurt at. Gamma goes from −1.18 to −9.25 — delta now moves about eight times as far per dollar.
  • Both climb together. Neither one is available without the other.
  • The 21-day mark is roughly where the second one starts to steepen on a 45-day trade.

It is a gamma rule wearing a time rule’s clothes.

Black-Scholes arithmetic from the specification above, with the stock at $95.50. Not a measured result.

Where it bites

The number does not travel

  • Twenty-one days on a 45-day trade is the back half of the position’s life.
  • Twenty-one days on a 60-day trade is a different fraction of it, and on a weekly it is meaningless.
  • The rule is quoted as an absolute and behaves as a proportion.
  • Anyone applying it to a tenor it wasn’t built for is guessing, however confidently.

And it is not free

  • Closing at 21 days gives up the fastest-decaying stretch of the trade — the part that pays most per day.
  • It also books losses on positions that would have recovered in the final weeks.
  • Whether what you avoid is worth what you give up is the entire question, and it is measurable.
What would settle it

One set of entries, run three ways: closed at 21 days, closed at a profit target, and held to expiry. Scored on expectancy per trade and on the worst drawdown, not on the share of trades that won. Anything short of that is two people quoting each other.

Common questions

Is the 21-DTE rule proven?

It is widely repeated, which is different. It rests on published research from one part of the retail options industry, and this site has not yet reproduced it.

Does it apply to 0-DTE trades?

Not in this form — there are no days left to leave. The equivalent is a clock time during the session, and it is managing exactly the same thing.

Should I close at 21 days even in profit?

That is what the rule says, and a profit target usually closes those trades first anyway. The date matters most for the positions that are neither won nor lost.

Why 21 and not 20 or 25?

There is nothing structural about the number. Gamma steepens gradually, not on a particular Tuesday. The precision of the number is the least defensible part of it.

How this shows up in our tests

No result on the 21-day rule is published here yet.

It sits inside the exit ladder run — the same entries closed seven ways. When it publishes, this entry will link to it and will state whether the rule earned its keep under our specification, including if the answer is no.

The mechanism

Gamma risk
near expiry

The exit

The time
exit

The hub

The seven ways
to exit