How to Choose an Office Chair Size for a Home Office

Choose a chair by the opening it has to pass through and the seat depth your legs need. A size letter is only useful after you know which arm option is on the listing.

The Canadian Centre for Occupational Health and Safety says elbows should stay close to the body and bend at about 90 degrees, with hands, wrists, and forearms straight and roughly parallel to the floor. Use that as the seated position when you measure. This page does not turn that into a body-height chart.

Measure three things

1. Seat depth you want. Sit back on a hard chair and measure from the backrest contact to a point short of the back of the knee. The front edge should support the thigh without pressing into the knee. Write the number in inches.
2. Seat height. In the same position, with feet supported, measure from the floor to the top of the seat. A useful chair has a published seat-height range that includes a height close to that number. CCOHS’s elbow position is the second check: once the seat is set, the underside of the elbow should be able to meet the desk.
3. Opening width. Measure the gap under or beside the desk where the chair has to roll, including the arms. If you will use the chair armless, measure the base and the seat. If you will use arms, measure the gap the arms must clear.

The published specs page

Herman Miller’s Aeron specs page, read on 2026-11-03, gives a separate dimension set for sizes A, B, and C, and again for each arm option. Order the row that matches the arm option, not just the letter.

Use the row that matches the arm option on the specs page you are ordering from.

When not to buy

Skip the Aeron, and skip any other chair, when:

• Your measured seat depth is not close to a published seat depth.
• The width of the arm option you want is wider than the opening you measured.
• The seat-height range does not reach the height you measured with your feet supported.
• You cannot sit in the chair, or in the same size, before it has to come through a doorway or up stairs you have not measured.

A showroom or a return window is the check this page cannot do. The chart only tells you which listing questions to ask.

The rest of the desk

Chair height and desk height are one setup. If you are also changing the desk, measure both elbow heights in how to measure a standing desk. If the keyboard is what crowds your wrists, go to how to choose a keyboard and mouse.