---
title: "20-20-20 Rule Timer for Eye Strain | Desk Blossom"
description: "A free 20-20-20 timer: every 20 minutes, look 20 feet (6 m) away for 20 seconds. Gentle cues, optional sound, and what the evidence says about eye strain."
url: https://deskblossom.me/20-20-20-rule-timer/
---

Eye strain from screens

# 20-20-20 rule timer

The 20-20-20 rule, from the American Academy of Ophthalmology: every 20 minutes, look at something at least 20 feet (about 6 metres) away for at least 20 seconds. Press start and the timer counts down your screen time, then tells you when to look away and when the 20 seconds are up. Think of it as a reminder to rest your eyes and blink, not a treatment: screens don’t cause permanent damage to your eyes, and the evidence for the exact numbers is thin.

## How to use the timer

1. Press **Start** when you sit down to work. The ring fills over 20 minutes of screen time.
2. When it turns pink and the blossom opens, look out of a window or across the room at something at least 20 feet (6 m) away, and blink a few times. The timer counts the 20 seconds for you.
3. It then starts the next 20 minutes on its own. **Pause** it for a meeting, **Break now** to take a break early, or **Reset** to start again.

**In a background tab.** The countdown is worked out from the clock, so it is always right when you come back to the tab. The cues are another matter: browsers slow timers in hidden tabs to save battery. Chrome, for example, checks them only once a minute after a tab has been hidden for five minutes, unless the page has made a sound in the last 30 seconds, and Firefox for Android may unload a background tab altogether. So a chime or notification can come up to a minute late. For dependable cues, keep this tab visible, for example in a small window beside your work. The tab’s title also shows the time left. If you turn on motion reduction in your system settings, the ring and blossom change without animating.

## What the evidence says about the 20-20-20 rule

The AAO recommends the rule for eye strain, and the UK HSE gives similar advice for screen users: look into the distance from time to time, and blink often. But the specific numbers have been studied very little.

- **One small trial found it helped while people used it.** Talens-Estarelles and colleagues (Contact Lens and Anterior Eye, 2023) gave 29 computer users with symptoms software that reminded them to follow the rule. After two weeks their eye-strain and dry-eye symptoms had improved, but the improvement was gone one week after the reminders stopped, and none of the measured signs of dry eye changed.
- **Another found 20-second breaks made no difference.** Johnson and Rosenfield (Optometry and Vision Science, 2023) had 30 young adults do a 40-minute reading task on a tablet four times, with 20-second breaks every 5, 10 or 20 minutes or no break. Symptoms rose in every session, and the breaks made no significant difference. The authors note this doesn’t rule out longer breaks or a different rhythm.

So the rule is a handy, harmless habit rather than a proven treatment. Regular breaks from the screen are still sensible: the HSE says short, frequent breaks are better than long, infrequent ones, for example 5 to 10 minutes every hour rather than 20 minutes every two hours. If 20 seconds feels too short, set a longer look-away time.

## Why screens strain your eyes

The AAO says we normally blink about 15 times a minute, but only 5 to 7 times a minute when using a computer or other screen, so the eyes dry out. Eye strain is more a symptom than a condition. Other causes the AAO lists:

- **Glare and lighting** that is too bright or too dim. The AAO suggests a matte screen filter to cut glare, and the HSE suggests a screen that doesn’t face windows or bright lights.
- **Glasses or contact lenses** with the wrong prescription.
- **Dry air,** or a heating or air-conditioning vent blowing on your face. The AAO suggests a humidifier if you’re often in a dry, warm room, and artificial tears when your eyes feel dry.
- **Screen position.** The AAO suggests sitting about 25 inches (64 cm) away with your gaze slightly downward; see the [monitor distance calculator](https://deskblossom.me/monitor-distance-calculator/).

Screen work does not cause permanent damage to the eyes: both the HSE and the AAO say so. It can still leave them tired, sore or blurry, and cause headaches.

Something to do with your 20 seconds? A slow breath or two works well alongside looking away; our sister site [Mellow Harbor](https://mellowharbor.cyou/) has gentle breathing timers.

## When to see an optometrist or a doctor

- **Eye strain that continues after you’ve sorted out your screen and lighting:** the AAO suggests seeing an eye doctor, who can check for dry eye and whether you need a new prescription. In the UK, start with an optometrist (optician).
- **Dry eyes that haven’t improved after a few weeks** of home treatment: the NHS says to see an optician or GP. A pharmacist can suggest eye drops in the meantime.
- **A painful red eye,** or a red eye while you wear contact lenses: the NHS says to contact a GP urgently or call 111.
- **Sudden changes in your sight,** such as wavy lines, flashing or loss of vision: the NHS says to call 999 or go to A&E straight away.
- **UK employees who use screens daily:** your employer must provide an eye test if you ask, and pay for basic glasses if you need them specifically for screen work.

**General information, not medical advice.** The timer is a habit tool. It doesn’t diagnose or treat any eye condition.

## Sources

All checked on 5 November 2026.

- American Academy of Ophthalmology: [Eye strain and sleepy eyes: how to prevent eye discomfort](https://www.aao.org/eye-health/diseases/what-is-eye-strain) (5 May 2023), for the 20-20-20 rule and causes, and [Computers, digital devices and eye strain](https://www.aao.org/eye-health/tips-prevention/computer-usage) (27 June 2024), for blink rates and screen distance.
- Talens-Estarelles C, Cerviño A, García-Lázaro S, Fogelton A, Sheppard A, Wolffsohn JS. [The effects of breaks on digital eye strain, dry eye and binocular vision: testing the 20-20-20 rule](https://doi.org/10.1016/j.clae.2022.101744). Contact Lens and Anterior Eye 46(2), 101744 (2023).
- Johnson S, Rosenfield M. [20-20-20 rule: are these numbers justified?](https://doi.org/10.1097/OPX.0000000000001971) Optometry and Vision Science 100(1), 52–56 (2023).
- Health and Safety Executive (HSE): [Working with display screen equipment (DSE): a brief guide](https://www.hse.gov.uk/pubns/indg36.pdf) (INDG36 rev4, 2013), [Work routine and breaks](https://www.hse.gov.uk/msd/dse/work-routine.htm) and [Eye tests for DSE users](https://www.hse.gov.uk/msd/dse/eye-tests.htm) (both updated 20 March 2025).
- NHS: [Dry eyes](https://www.nhs.uk/conditions/dry-eyes/) (reviewed 6 January 2025).
- Background timers: MDN Web Docs, [setTimeout(): timeouts in inactive tabs](https://developer.mozilla.org/en-US/docs/Web/API/Window/setTimeout) (last modified 26 October 2026); Chrome for Developers, [Heavy throttling of chained JS timers beginning in Chrome 88](https://developer.chrome.com/blog/timer-throttling-in-chrome-88) (January 2021).

## Questions

**Does the 20-20-20 rule actually work?**

The evidence is thin. One small trial found eye-strain symptoms improved while people used 20-20-20 reminders, but not after they stopped; another found 20-second breaks made no significant difference. It is a harmless habit that reminds you to look away and blink.

**Why 20 feet?**

It is the distance in the AAO’s version of the rule, about 6 metres: far enough to look well beyond your screen. Out of a window or across a room both work. Johnson and Rosenfield point out that there is relatively little peer-reviewed evidence behind the rule’s numbers.

**Can screens damage your eyes?**

Not permanently: the HSE and the AAO both say screen use doesn’t cause permanent damage. It can cause tired, dry or sore eyes, blurred vision and headaches, which usually ease with breaks and a better set-up.

**Will the timer work if I switch tabs?**

Yes, while the page stays open: the countdown follows the clock, and cues still come, though browsers may delay them by up to a minute in a hidden tab. Keep the tab visible for cues on time.

**When should I see an optometrist about eye strain?**

If your eyes still feel strained after fixing your screen position, lighting and breaks, or if you think your glasses are out of date. Get urgent help for a painful red eye or sudden changes in your sight.