What is the 90/20 rule?

The 90/20 rule is based on the scientific observation that the human brain naturally cycles through roughly 90-120 minute periods of peak focus, called ultradian rhythms. You work without interruption for 90 minutes, then take a full 20-minute rest break to let your brain clear mental fatigue.

What is an ultradian rhythm?

An ultradian rhythm is a biological cycle that repeats in less than 24 hours. Our focus and alertness naturally rise and fall in roughly 90-120 minute waves throughout the day; this method aims to align your work sessions with that natural wave.

How is 90/20 different from Pomodoro and 52/17?

90/20 uses the longest work block of the three (90 minutes) and is ideal for tasks that need deep, uninterrupted focus, like writing, coding, or complex problem-solving. Pomodoro and 52/17 offer shorter, more frequent blocks.

Who is the 90/20 method best suited for?

It's ideal for people who can go deep without losing focus, don't want frequent interruptions, and prefer working in large blocks. If short intervals help you stay focused, Pomodoro may suit you better.

Tools/🎯 Productivity/90/20 Ultradian Rhythm

90/20 Ultradian Rhythm

90 minutes of deep focus, 20 minutes of complete rest — a work rhythm that follows the brain's natural peak-focus cycle.

Version 1.0 · Last Updated: August 3, 2026 · Maintained by ToolLarder

The 90/20 Ultradian Rhythm is also known as the 90/20 Rule or the Ultradian Rhythm Technique. It's based on the brain's natural biological cycle (roughly 90-120 minute peak-focus periods) and offers the longest, deepest work blocks of the three techniques.

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Other Rhythms

Pomodoro Timer

Work for 25 minutes, take a 5-minute break; take a long break every 4 sessions with the Pomodoro Technique.

The 52/17 Method

52 minutes of complete focus, 17 minutes of complete rest — the balanced work rhythm used by the most productive workers.

Eisenhower Matrix

Sort your tasks by urgency and importance into four quadrants; get clear on what to do now, schedule, delegate, or drop.

90/20 Ultradian Rhythm

Other Rhythms

Frequently Asked Questions