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The 24 hour rule: what waiting one day actually does

By , who built Keep the Diff

The 24 hour rule is the simplest impulse control method there is: when you want to buy something that is not a necessity, wait a day. If you still want it tomorrow, buy it.

It works more often than advice this simple has any right to. It is also incomplete in a specific way that stops most people from sticking with it, which is the part this article is about.

Why one day is enough

The urge to buy something and the wish to own it are two different feelings that arrive at the same moment, and only one of them lasts.

The urge is a response to the situation you are standing in: the shop, the tab, the recommendation, the sale ending tonight. It is sharp, it is specific, and it fades on its own within hours once you are somewhere else. The wish to own the thing is slower and much steadier, and it is still there tomorrow.

Waiting a day does not test your discipline. It waits out the first feeling so you can see whether the second one exists. Most of the time it does not, and you find you were not buying a jacket, you were buying your way out of twenty minutes of boredom.

Where it fails

Three cases, and they are worth knowing in advance.

  • A genuine deadline. Sometimes the sale really does end tonight and the thing really is one you were going to buy anyway. The rule has no answer here, and treating a real deadline as a fake one is its own kind of expensive.
  • The rule becomes a queue. You wait a day, buy it, and repeat. The purchase happens either way, just one day later, and now you feel deliberate about it. That is the failure people notice least.
  • Small amounts. Nobody waits a day over a four dollar coffee, and the four dollar decisions are most of them. A rule that only covers the rare large purchase misses where the money actually goes.

The step almost everybody leaves out

Here is what happens when the rule works. You want the thing. You wait. Tomorrow you do not want it. You do nothing.

Nothing is the problem. A purchase leaves a receipt, a line on a statement, a package by the door. Not buying leaves no trace at all. So the successful outcome of the 24 hour rule is completely invisible, and the unsuccessful one is a nice new thing you can see.

Do that for a month and the honest impression you are left with is that the rule did not do much, because the only evidence you have is of the times it failed.

The missing step is to record the decision. Write down what you were about to spend, and what you actually spent, which is usually zero. Now waiting produces something: a number, and a number that adds up.

What that changes

Two things, and the second one is bigger than it sounds.

First, it makes the method visible. Nine waits at thirty dollars is two hundred and seventy dollars you still have, and seeing that total is the difference between believing the rule works and knowing it does.

Second, it gives you something to do at the moment of temptation. Willpower advice asks you to sit still and resist. That is hard, and doing nothing is a strange thing to practice. Logging the decision is an action, it takes a few seconds, and it converts the moment from a test you might fail into a thing you just did.

The same idea is worked through at more length in stop impulse buying by recording what you didn't buy.

The version worth actually running

  1. Something catches you. Do not buy it yet.
  2. Write down what you were about to spend. Ten seconds, right there.
  3. Wait a day.
  4. If you still want it, buy it, and nothing bad has happened. That is the rule working exactly as intended.
  5. If you do not, record what you actually spent, which is zero, and keep the difference.

Step four matters as much as step five. A rule that treats buying the thing as a failure is a rule you will stop using, because sooner or later you will buy the thing. The 24 hour rule is not a promise never to spend. It is a way of finding out which of the two feelings you were having.

Keep the Diff is built around steps two and five. You log what you were ready to spend and what you actually spent, and the difference is recorded as money you kept. It is free on iPhone, iPad, Mac, Apple Watch, Windows and Android, with no account and no bank connection, and you can try it in your browser first.

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