Herman Miller Aeron sizes A, B and C explained

The three sizes

Size A is the smallest, with a narrower, shallower seat and a shorter back. It suits smaller adults, for whom a B seat would be too deep. Size B is the medium size and the one most offices buy, suiting a wide range of average heights and builds. Size C is the largest, with a wider, deeper seat and a taller back, aimed at tall and heavier users.

Herman Miller publishes a sizing chart with suggested height and weight ranges for each size. Use it as a starting point, then check seat depth: when you sit right back, there should be a gap of a few fingers between the seat edge and the back of your knees.

How to find the size on a used chair

Most Aerons have the size letter printed on a label under the seat or moulded into the back of the seat frame. Some sellers list it in the title, as with the renewed size B chair in our mesh guide. If you cannot see it, measure the seat and compare with Herman Miller's published dimensions.

Listings for replacement seats give useful clues. A replacement seat for the classic size B is listed at 20.25 inches wide by 18 inches deep, about 51.4 by 45.7 cm. That listing also notes it does not fit the remastered Aeron, so check which generation you have before buying parts.

When buying online, ask the seller for a photo of the label and of the seat from above. A worn or replaced seat may come from a different size, so also check that the seat and back look matched in width. If the listing only says Aeron with no size, treat the size as unknown until confirmed.

Weight limits

Weight limits differ by size and listing. Size C is the one recommended for heavier users and is commonly quoted at up to 350 lb, about 159 kg. The renewed size B listing in our mesh guide states a maximum of 110 kg, and a replacement size B seat is listed at 250 lb, about 113 kg. Because figures vary between sources, check Herman Miller's current sizing guide for the chair you are buying, and choose a size with headroom. Our US spec converter turns pounds into kilograms.

See chairs rated over 180 kg →

Aeron settings worth knowing

Once the size is right, set the chair up. The main controls on most Aerons are:

• Seat height lever on the right side
• Tilt tension knob under the front of the seat
• Tilt limiter, which sets how far back the chair reclines
• Forward tilt, on chairs that have it
• Lumbar pad or PostureFit support, depending on generation
• Arm height and pad pivot, and more on some specifications

Choosing between sizes

If you are between sizes, think about seat depth and width. A seat that is too deep presses behind the knees; one that is too narrow lets the frame edge press on your thighs. Tall users with long thighs often prefer C; slim users of average height usually find B fits. If you cannot try one, the Embody or a Steelcase chair with a sliding seat is more forgiving. Our Aeron vs Embody comparison covers that choice.

Compare chairs for tall people →

Frequently asked questions

Which Aeron size am I? Most average adults fit size B. Smaller people suit A, and tall or heavier people suit C. Check Herman Miller's sizing chart and test seat depth.

What is the Aeron size C weight limit? It is commonly quoted at 350 lb, about 159 kg. Confirm with Herman Miller for the specific chair.

Can I change an Aeron's size? No. The frame, seat and back are size-specific. You would need a different chair.

Are classic and remastered Aeron parts interchangeable? Not always. Some replacement seats state they fit the classic Aeron only.