90 Minute Timer

90 minutes at a glance

In seconds	5,400 seconds
In hours	1.5 hours
In milliseconds	5,400,000 ms
Written as	01:30:00

On a timesheet 90 minutes is 1.5 hours, or 90 minutes, or 1.50 hours. In code it is 5,400,000 milliseconds, usually written 90 * 60 * 1000 rather than as the literal number.

What fits into 90 minutes

• One sleep cycle
• One ultradian focus wave
• A football match

Ninety minutes is roughly one sleep cycle and, according to the ultradian rhythm literature, roughly one natural wave of alertness. It is the longest block most people can sustain before performance falls regardless of willpower.

Running a 90 minute block well

1. Treat it as a container, not one pushAt an hour or more, plan two or three efforts inside the block with pauses between them rather than one continuous stretch.
2. Sort out fuel and water firstPast forty-five minutes the limiting factor stops being attention and starts being blood sugar and hydration.
3. Expect a dip in the middleMost long sessions have a flat stretch where the work stops feeling interesting. It is not a signal to stop.
4. Plan the endingDecide before you start what finished looks like, or a long block quietly becomes an afternoon.

It is also a football match, a feature-length rehearsal and the standard length of a serious deep work session in most of the writing on the subject.

Other lengths

• 1 Minute TimerOne minute is a plank, a rinse of the kettle, a held…
• 2 Minute TimerTwo minutes is the classic tooth-brushing block and…
• 3 Minute TimerThree minutes covers a boxing round, a soft-boiled…
• 4 Minute TimerFour minutes is one full Tabata block: eight rounds…
• 5 Minute TimerFive minutes is the standard short break, and long…
• 6 Minute TimerSix minutes suits a mobility flow, a warm-up jog or…
• 7 Minute TimerSeven minutes is the length of the original…
• 8 Minute TimerEight minutes is two four-minute rounds, or one slow…
• 10 Minute TimerTen minutes is the sweet spot for a first meditation…
• 12 Minute TimerTwelve minutes covers a Cooper test run or three…
• 15 Minute TimerFifteen minutes is short enough to start without…

Need a little more or less time? Try the 75 minute timer or the 120 minute timer.

Questions people ask

Why is 90 minutes significant?

It approximates both a full sleep cycle and one ultradian cycle of alertness during the day. Working in ninety minute blocks with real recovery between them lines effort up with the body's own rhythm.

How many seconds are in 90 minutes?

There are 5,400 seconds in 90 minutes, because every minute contains 60 seconds.

Can I pause the 90 minute timer and carry on?

Yes. The space bar or the pause button stops it where it is, and pressing again resumes from the same point rather than restarting at the top.

Will the timer survive a screen lock?

The countdown itself will, because it reads the system clock. The alarm needs the tab open, so on phones a wake lock is requested to keep the display on.

Should I break a long block into stages?

Usually yes. Two or three efforts inside the block, with short pauses, hold quality better than one unbroken stretch of the same total length.

Is the 90 minute timer free to use?

Yes, for personal and commercial use, with no sign-up and no limit. Use it in classrooms, gyms and streams without asking.