25 minute timer

Because it is long enough to get somewhere and short enough to start. The number comes from Francesco Cirillo, who set a kitchen timer to 25 minutes while studying in the late 1980s — it was the interval his tomato-shaped timer happened to make easy, and it stuck.

There is no research showing 25 beats 20 or 30. What holds up is narrower: switching between tasks costs you, and a deadline you can see makes starting easier. Twenty-five minutes is a sensible default, not a finding.

1. Decide the one thing you will work on. Not a list — one.
2. Press start and leave everything else alone until the chime.
3. If something pulls at you, write it down rather than following it.
4. When it rings, take five minutes away from the screen.

The timer keeps correct time if you switch tabs or your machine sleeps — it reads the clock rather than counting ticks, so a backgrounded tab cannot lose you minutes. The countdown also appears in the tab title, which is where you will be looking when the timer itself is behind another window.

A short chime, and the option of a five-minute break. Take it. Skipping the break because the work is going well is the single most common way this stops working by the third hour — the break is what makes the next session possible.

Four rounds of 25 and 5 is about two hours of real work, which is more than most days contain. After the fourth, take fifteen to thirty minutes properly.

It will not fit everything. Work with a slow warm-up — writing, code, anything that needs you to hold a lot in your head — often suits 50 minutes with a 10-minute break. Admin, revision and anything you have been avoiding usually suit 25 or less.

The timer above takes a custom length, so you can try 50 or 15 without any setup — and the study timer opens on 50/10 if that is the rhythm you are after. The question worth asking is not which length is best, but which one you actually finish: a 50-minute session abandoned half the time is worth less than a 25-minute one you complete.