Herman Miller Aeron Size A, B, C — how to identify, and what each is worth
The Aeron comes in three sizes — Size A (small), Size B (medium), Size C (large). Most UK Aerons are Size B, but if you do not know which size you have, this is how to check and what each is worth in 2026.
How to find the size stamp
Flip the chair upside down. There is a small stamp on the bottom of the seat pan, near the centre, with a single letter — A, B, or C. That is the size. Sometimes the stamp is on the underside of the seat pan, sometimes on a small label inside the rear lip. Check both.
If the stamp is illegible or missing (rare but possible on chairs from before 2003), measurements help: Size A seat pan is roughly 41cm wide × 39cm deep, Size B is 46cm × 43cm, Size C is 51cm × 47cm. Sit on the chair for 30 seconds — if your thighs are uncomfortably squeezed, you are probably on a Size A; if there is a noticeable gap behind your knees, you are probably on a Size C.
Size B is by far the most common — and the easiest to resell
Around 75% of UK office Aerons are Size B. It is the size specified by default in most corporate fit-outs because it covers roughly 5'2" to 6'2" — the bulk of the working population. The secondary market also skews heavily Size B, which means a refurbished Size B Aeron typically resells within 7–14 days of refurb.
Size A and Size C each make up roughly 10–15% of UK Aerons. The secondary market for them is genuinely real but thinner — refurbed Size A chairs typically resell in 14–21 days, Size C in 21–28 days. We absorb that timing risk; sellers see the same headline rate either way.
Pricing — same headline across all three sizes
Aeron Classic, all sizes: £180 per chair Grade A. Aeron Remastered, all sizes: £250 per chair Grade A. We do not discount for Size A or Size C even though they are slower to resell.
The reason: a steady supply of A and C across our buyback flow keeps our reseller relationships easier to maintain. Home-office buyers come in all heights, and a refurbisher who can offer Size A and C is more useful to a buyer pool than one who only offers Size B. Paying the same rate across sizes keeps that supply flowing.
What is the rarest Aeron variant?
Aeron Size A in Polished Aluminium, with PostureFit SL and matched Pellicle, in any Remastered configuration — extremely rare. We see maybe two a year. Premium-configuration uplift applies (~£270–£280 per chair).
The most common variant by far: Aeron Classic Size B, graphite base, standard PostureFit, fully-adjustable arms. Roughly 50% of every UK Aeron buyback we do is this configuration. Standard £180 per chair.
Mixed sizes in one quote
A typical 80-Aeron UK office buyback breaks down as roughly 60 × Size B + 12 × Size A + 8 × Size C. We line-item by size only if the price differs (it does not, in this case) — otherwise we line-item by generation (Classic vs Remastered) and quote one number per generation.
If you are clearing 80 Aerons and you do not know the size mix, do not worry about it. We will discover the sizes on collection day and the per-chair rate is the same across all three. The total BACS lands as quoted.
Should I keep a Size A or Size C if I am downsizing?
If you have one in your home that fits you perfectly, keep it. Size B Aerons do not feel right on someone built for an A or C — the lumbar height and seat depth are calibrated to the size. A Size B Aeron used by a Size C person for 8 hours a day causes discomfort that defeats the point of buying an Aeron.
From a pure resale-value perspective, it does not matter which size you keep — they all command the same buyback rate. So pick the one that fits.
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