What is an actogram?

Short answer: An actogram is a chart of activity across many days, drawn with one row for each day, so the daily rhythm of rest and activity can be seen at a glance. Dark marks show when you were active and blank space shows rest. When the marks line up from one row to the next, the body clock is keeping steady time with the 24-hour day.

How do you read an actogram?

Each row is one day, with the 24 hours running from left to right, and the next day sits just below. Dark bars mark activity in short time slices, often a few minutes long, and a taller bar means more activity in that slice.

Then look down the page rather than across it. If the active block starts at about the same time every day, its edge forms a straight vertical line and the rhythm is steady. Ragged edges point to irregular days, and marks scattered through the rest block point to broken rest. To try this with your own days, see how to find your circadian rhythm.

Why are actograms often double-plotted?

A double-plotted actogram shows two days on every row. Row one holds day 1 and day 2 side by side, row two holds day 2 and day 3, and so on, so each day appears twice.

The reason is practical. A night of sleep or an evening of activity often runs past midnight, and on a single-plotted chart it gets cut in two at the edge of the row. Plotting each day twice keeps those stretches whole, which makes the rhythm much easier to see.

What does an actogram show about circadian rhythms?

It shows whether the body clock is in step with the outside day. Under a normal cycle of light and dark, the active block starts at about the same time each day. When animals are kept away from time cues, the clock runs on its own, which scientists call free-running, and its cycle is rarely exactly 24 hours. A common laboratory mouse strain kept in constant darkness has an internal day of about 23.7 hours, so its activity starts a little earlier each day and the band slants to the left.

The chart comes from animal research with running wheels. In 1922 the American scientist Curt Richter published a study of how rats ran by day and by night, and the running wheel became a standard tool for measuring activity rhythms. Labs still count the turns of the wheel and plot them as an actogram.

What does a drifting pattern mean in people?

A steady drift means the body clock is running on its own cycle instead of being reset each day. In people that cycle is a little longer than 24 hours, and in a carefully controlled lab study the human internal day averaged 24.18 hours. Without daylight to reset the clock each morning, activity would start slightly later each day and the band on an actogram would slant to the right.

This is what happens in non-24-hour sleep-wake rhythm disorder, which is common in people who are completely blind. Sleep times become later and later, until sleep can fall at noon instead of at night. The same chart can now be made for anyone, and researchers have drawn actograms from everyday wearables such as the Apple Watch. To see how far that data can go, read whether a smartwatch can track your circadian rhythm.

How Actogram looks at this

Actogram takes its name from this chart. It is a MedTech company registered in London, with its team in Barcelona, and its focus is the body clock.

It reads the daily rhythm of rest and activity from ordinary minute-level step counts from a phone or watch, with no heart rate and no sleep stages. It reads the rhythm from the daytime activity pattern, not only from night sleep. Today its tools are for research and wellness use and do not diagnose, treat or prevent any condition.

Sources

• A guideline for analyzing circadian wheel-running behavior in rodents under different lighting conditions, Biological Procedures Online, 2005
• Curt P. Richter, Biographical Memoirs Volume 65, National Academy of Sciences, 1994
• Stability, precision, and near-24-hour period of the human circadian pacemaker, Science, 1999
• Circadian Rhythm Disorders: Types, National Heart, Lung, and Blood Institute, 2022
• A method for characterizing daily physiology from widely used wearables, Cell Reports Methods, 2021

General information, not medical advice. If sleep or tiredness problems affect your daily life, talk to a doctor. Reviewed 6 November 2026 by the Actogram team.