How to Adjust Your Computer Chair for Proper Posture | Ergonomics That Work

Proper posture starts with a chair set so your feet rest flat, knees sit near hip height, and your lower back is supported by the lumbar curve.

Most people sit in a chair the way it comes out of the box — and then wonder why their back aches by noon. The fix for poor seated posture isn’t buying a fancier chair; it’s spending ten minutes adjusting the one you already own. The right setup follows a simple order: seat height, seat depth, backrest, then armrests last. Between a better-positioned existing chair and a comfortable new one, posture depends far more on adjustment than on price — though if your current chair lacks the controls to get this right, a better-designed model from our tested pick of the best chair for computer use may be worth the upgrade.

Set the Seat Height First

Seat height is the foundation — every other adjustment builds on it. Stand in front of the chair and raise or lower the seat so its highest point sits just below your kneecap. Sit down and check the angles.

With your back against the backrest, your feet should rest flat on the floor with thighs parallel to it, as the Mayo Clinic advises. Your knees should sit at hip height or slightly lower. If your feet dangle, use a footrest rather than raising the seat and forcing your shoulders up. Hips slightly higher than knees is fine when your desk height demands it.

Check Seat Depth and Backrest

Seat depth is the distance from the back of the seat to its front edge — and it’s the adjustment people skip most often. Sit with your back against the backrest and make a fist. You should have roughly a clenched fist of clearance between the seat edge and the backs of your knees, per the Canadian Centre for Occupational Health and Safety. No clearance means the seat pan is pressing into the backs of your knees, which can restrict circulation over a long day.

Set the backrest height and depth so its lumbar curve fits into the hollow of your lower back. The support should sit naturally against the curve, not push into it. Then set the backrest angle to a comfortable recline — commonly 100° to 110°, with sources ranging from 90° to 120°. Sit all the way back so your spine is supported; perching on the front edge defeats every other adjustment you’ve made.

Adjust Armrests Last and Keep the Desk Close

Armrests are the most common posture saboteur. They should let your elbows rest gently with shoulders relaxed, per CCOHS guidance — which means elbows near 90 degrees and shoulders nowhere near your ears.

If your armrests force your shoulders up, push you away from the desk, or block your keyboard position, drop them or remove them entirely. A chair without armrests beats one that ruins your shoulder position. Keep the keyboard and mouse close enough that your forearms stay roughly parallel to the floor and your shoulders stay relaxed, and ensure your elbows rest near a right angle as you type.

For a visual reference of how the ideal setup should look, this graphic demonstrates the correct seated posture.

Common Mistakes That Ruin Good Adjustments

Three mistakes undo most proper chair adjustments. Sitting too far forward on the seat pan instead of back against the backrest eliminates lumbar support. A seat height that forces your feet to dangle or your shoulders to elevate strains the entire upper body. And armrests that lift the shoulders or block close desk access create the exact tension you’re trying to eliminate.

When your desk height doesn’t cooperate, use a footrest or adjust the desk rather than accepting shoulder strain. These are general office-ergonomics guidelines for seated computer work, not medical advice — if you already have back pain, consult a professional.