Chair Adjustment 101: Seat Height, Depth, and Lumbar Support

Most people sit in an expensive chair they've never actually adjusted. The levers under the seat aren't decoration — set correctly, they're the difference between neutral, comfortable sitting and a sore lower back by lunch. Here's how to dial in every adjustment, top to bottom.

Key chair parts and what they do

A good task chair has four adjustments that matter: seat height, seat depth (how far the seat slides forward/back), backrest angle and lumbar support, and armrest height. Each one targets a different part of your sitting posture, and they interact — so set them in order, starting from the floor up.

Setting seat height and foot position

Start here, because it determines everything above it. Raise or lower the seat until your feet rest flat on the floor with your knees roughly level with your hips and thighs parallel to the ground. Your elbows should then land near desk height. If the desk forces the chair so high that your feet dangle, add a footrest rather than sitting with unsupported legs — dangling feet drag your posture forward all day.

Dialing in backrest angle and lumbar support

Your lower back has a natural inward curve, and the chair should support it rather than let you slump into a C-shape. Slide or inflate the lumbar support so it fills that curve. Set the backrest to a slight recline — around 100–110 degrees — which loads your spine less than bolt-upright. If your chair lacks lumbar support, a small rolled towel at belt height does the job. A neutral spine here is what prevents the slow slide into forward head posture.

Armrest height and width

Set armrests so your shoulders relax and your forearms rest lightly with elbows near 90 degrees — not so high they hike your shoulders up, not so low you lean. If armrests stop you pulling close to the desk and force you to reach, lower them or move them out of the way. Reaching for the keyboard is worse than no armrests at all.

Checking comfort over a full day

A chair that feels fine for five minutes can ache after five hours, so judge your setup across a full day and tweak. And remember — no chair setting beats getting up: the best posture is the next one, so pair good adjustment with frequent movement. A quick run through our posture score calculator and the guide to desk posture and tech neck ties it together.

The bottom line

Work from the floor up: seat height so feet are flat and elbows reach the desk, seat depth with a few fingers behind the knees, lumbar support filling your lower-back curve, and armrests that let your shoulders drop. Then recline slightly, move often, and let the chair do its job.