If you are looking up the best posture for sitting at a computer, start with where the screen, chair, keyboard, and feet are. The OSHA computer workstations eTool says there is no single correct posture or arrangement of components that will fit everyone. It lists basic design goals to consider when setting up a computer workstation or performing computer-related tasks. The sections below follow those goals, then the monitor and position pages in the same eTool.

Desk setup checklist

The figure on the OSHA computer workstations eTool lists these design goals:

Top of monitor at or just below eye level.
Head and neck balanced and in-line with torso.
Shoulders relaxed.
Elbows close to body and supported.
Lower back supported.
Wrists and hands in-line with forearms.
Adequate room for keyboard and mouse.
Feet flat on the floor.

Where to put the monitor

The monitors page of the same eTool adds placement details:

Put the monitor directly in front of you and at least 20 inches away.
Place the monitor so the top line of the screen is at or below eye level.
Place the monitor perpendicular to a window.

OSHA says the preferred viewing distance is generally between 20 and 40 inches (50 and 100 cm) from the eye to the front surface of the computer screen. The top of the monitor should be at or slightly below eye level. The center of the computer monitor should normally be located 15 to 20 degrees below horizontal eye level. Text size may need to be increased for smaller monitors.

A neutral sitting position

The good working positions page describes neutral body positioning as a comfortable working posture in which your joints are naturally aligned. For computer work, that page lists:

Hands, wrists, and forearms are straight, in-line and roughly parallel to the floor.
Head is level, forward facing, and balanced. Generally it is in-line with the torso.
Shoulders are relaxed and upper arms hang normally at the side of the body.
Elbows stay in close to the body and are bent between 90 and 120 degrees.
Feet are fully supported by the floor or a footrest may be used if the desk height is not adjustable.
Back is fully supported with appropriate lumbar support when sitting vertical or leaning back slightly.
Thighs and hips are supported and generally parallel to the floor.
Knees are about the same height as the hips with the feet slightly forward.

OSHA describes four reference postures as examples of body posture changes that all provide neutral positioning for the body: upright sitting, standing, declined sitting, and reclined sitting.

Upright sitting: the torso and neck are approximately vertical and in-line, the thighs are approximately horizontal, and the lower legs are vertical.
Standing: the legs, torso, neck, and head are approximately in-line and vertical with feet slightly apart. The user may also elevate one foot on a rest while in this posture.
Declined sitting: the thighs are inclined with the buttocks higher than the knee, and the angle between the thighs and the torso is greater than 90 degrees. The torso is vertical or slightly reclined and the legs are vertical. This position should not inhibit the ability to easily reach the keyboard or view the monitor.
Reclined sitting: the torso and neck are straight and recline between 105 and 120 degrees from the thighs.

Change position through the day

The good working positions page says to change your working position frequently throughout the day:

Make small adjustments to your chair or backrest.
Stretch your fingers, hands, arms, and torso.
Stand up and walk around for a few minutes periodically.
Perform some of your tasks while standing. The examples OSHA gives are computing, reading, phone, and meetings.

Stretching your fingers, hands, arms, and torso is optional. Stop if anything hurts.

Short breaks you can time

A short look-away is a separate habit from the desk setup. The American Academy of Ophthalmology suggests the 20-20-20 rule: every 20 minutes, look at an object at least 20 feet away for at least 20 seconds. That is what the Academy suggests for a short look-away break. It is not a cure.

If you want that count in the browser, open the eye break timer. It counts 20 minutes, asks you to look about 20 feet away for 20 seconds, then starts the next 20 minutes. It only runs while that browser tab stays open. The guide on how to reduce eye strain and improve posture at your desk covers that look-away and a few seat checks.

For a longer work block, the Pomodoro timer counts 25 minutes of work, then a 5-minute break. After four work blocks it counts a 15-minute break. It only runs while that browser tab stays open. How often should you take breaks at work compares that pattern with the 20-second look-away and a longer break you choose.

How CapyBreaks helps

The eye break timer and the Pomodoro timer stay in the browser. CapyBreaks is a desktop break reminder app for Mac and Windows. It reminds you without a browser tab. An animated capybara shows up when a reminder is due. The posture check asks you to notice how you are sitting. It does not move your monitor or your chair.

Why use a break reminder app on Mac or Windows covers what to check before you install one.

These reminders are on when you first open the app:

A general break, every 60 minutes.
A reminder to drink water, every 30 minutes.
A reminder to stretch, every 45 minutes.
A posture check, every 20 minutes. It asks you to notice how you are sitting.

Eye Breaks are off until you turn them on. That reminder prompts you to look away, and its interval starts at 20 minutes. You can change any interval, or turn a reminder off.

Working hours are off until you turn them on. The starting schedule is weekdays from 9:00 to 17:00. When working hours are on, reminders show only during the hours you set.

Personal is $14.99 once for up to 3 devices, with a 7-day trial. Team is $9.99 per seat. Windows installs from the Microsoft Store. The Mac download is an Apple-silicon DMG. The 7-day trial starts the first time you open the app. You do not need a CapyBreaks account.

A reminder that comes due while the microphone is in use, or while a fullscreen app is active, is skipped and the timers start over. On Windows, reminders also pause when Windows reports presentation mode. On Mac, a presentation in a window that does not fill the screen does not by itself pause reminders. Default idle detection skips a due reminder after 5 minutes without keyboard or mouse and starts the timers over. A screen share by itself does not pause reminders.

CapyBreaks is a reminder app. It will not fix back pain, headaches, or an eye condition.

The download buttons below are the same ones as the homepage. On a Mac they download the Apple-silicon DMG. On Windows they open the Microsoft Store.

The Best Posture for Sitting at a Computer: Desk Setup Checklist