How Can I Tell Which Size Aeron Chair I Have?

Every Herman Miller Aeron is made in one of three sizes: A (small), B (medium) or C (large). You need to know which one you have before ordering size-specific parts such as seat mesh, a seat pan or a back rest, and the quickest way to check is the “bump method”: a few small bumps moulded under the back frame that tell you the size by touch. It works on both the Aeron Classic and the Aeron Remastered.

How to check your Aeron size

1. Find the Herman Miller stamp

Turn the chair round and look at the top of the back frame. The Herman Miller logo is stamped near the top centre.

2. Feel under the frame

Put your fingertips under the edge of the frame, just below the stamp, and press gently. You will feel one or more small raised bumps.

3. Count the bumps

The number of bumps is the size of your chair:

Two bumps under the frame: this chair is a size B.

Why the size matters

• Parts: seat mesh, complete seat pans and back rests are made for one size only, and our taller gas lift fits sizes B and C only. Arm pads, casters, the lumbar pad and most other parts fit all three.
• Comfort: the right size lets you sit with your feet flat, knees at about a right angle and your back fully supported.
• Buying second-hand: sellers do not always list the size, so a quick check tells you whether a chair will fit you before you buy.

Still not sure?

If the bumps are hard to feel, look for the label under the seat: on most chairs it shows the size letter. You can also measure the seat from front to back and compare it with the table above. Or email a photo of the underside of the back frame to info@hmchairs.co.uk and we will tell you which size you have.