If you are looking to buy a Herman Miller Aeron, the first decision you have to make is choosing the right size. Unlike most ergonomic chairs that rely on a one-size-fits-all approach with adjustable sliding seats, the Aeron comes in three distinct sizes: Size A (Small), Size B (Medium), and Size C (Large).
Choosing the correct size is critical. The Aeron's iconic 8Z Pellicle mesh suspension system and rigid frame mean that if you buy the wrong size, the chair will not support you properly. A chair that is too small will pinch your hips and restrict circulation in your legs. A chair that is too large will press into the back of your knees and fail to support your lower back.
The thing most size guides get wrong is treating this as a height question. Herman Miller's own size and fit reference sizes the Aeron on height and weight together — you find the point where your height and your weight intersect. Two people the same height can take different sizes. This guide uses Herman Miller's current chart, dated June 2026. If you are still deciding whether the Aeron is the right chair for you at all, rather than which size to take, our full Aeron review covers what it does well and where it does not suit.
How Herman Miller actually sizes the Aeron
The Aeron comes in three sizes (A, B, C) to accommodate different body types
Herman Miller publishes a size and fit chart rather than a list of height brackets. In its own words, "height and weight are key indicators of suitable chair-size choice", and you choose by finding "the point of intersection for your height and weight." The chart runs from 142 cm to 200 cm and from 41 kg to 181 kg, and it has five regions: Size A, Size A or B, Size B, Size B or C, and Size C.
Read across from your height, then along to your weight. Where you land is your size.
| Your height | Size A | Size A or B | Size B | Size B or C | Size C |
|---|---|---|---|---|---|
| 142–150 cm | 41–54 kg | 58–72 kg | 77–131 kg | 136–145 kg | 149 kg and over |
| 152–155 cm | 41–54 kg | 58–72 kg | 77–95 kg | 99–145 kg | 149 kg and over |
| 157 cm | — | 41–72 kg | 77–95 kg | 99–122 kg | 126 kg and over |
| 160–175 cm | — | 41–72 kg | 77 kg | 81–113 kg | 117 kg and over |
| 177 cm | — | — | 41–77 kg | 81–113 kg | 117 kg and over |
| 180–192 cm | — | — | 41–68 kg | 72–122 kg | 126 kg and over |
| 195–200 cm | — | — | 41–68 kg | 72–86 kg | 90 kg and over |
Three things in that table surprise almost everyone.
- Size B covers the entire height range, 142 cm to 200 cm. It is not the "medium person" size. It is the size most people of any height land on.
- Size C is driven more by weight than by height. A very tall, light person takes a Size B. Someone of average height and a heavier build can land in Size C.
- Size A is a narrow specification. On Herman Miller's chart it applies at 142 to 155 cm and 41 to 54 kg. Outside that, even a short user moves into A-or-B or straight to B.
Where you land in a shared region — "A or B", or "B or C" — Herman Miller's answer is Size B. Its reference says the B-size chair is designed to fit a broad range of people, and recommends it for users who fall in the A/B or B/C category.
If you are close to a boundary, ring us on 02 9640 0642 and we will talk it through, or come and sit in all three at the showroom. A chart is a starting point, not a fitting.
Weight ratings
Chair Dinkum’s stated maximum user weight for the Aeron we sell is 136 kg for Size A and 159 kg for Sizes B and C. Herman Miller’s current technical documents publish a higher 181 kg rating for Size C; our stated maximum stays at 159 kg. These are ratings rather than selection brackets — use the chart above to choose the size, and treat the rating as the ceiling that size is built to.
The measurements, size by size
| Specification | Size A (Small) | Size B (Medium) | Size C (Large) |
|---|---|---|---|
| Seat Depth (fixed, not adjustable) | 406 mm | 432 mm | 470 mm |
| Seat Height Range | 366 to 490 mm | 376 to 579 mm | 401 to 579 mm |
| Overall Width (arms in to arms out) | 698 to 744 mm | 719 to 772 mm | 719 to 803 mm |
| Overall Depth | 686 to 698 mm | 698 to 719 mm | 698 to 719 mm |
| Overall Height | 870 to 978 mm | 933 to 1045 mm | 1016 to 1153 mm |
| Arm Height | 190 to 292 mm | 190 to 292 mm | 190 to 292 mm |
| Maximum user weight | 136 kg | 159 kg | 159 kg |
Dimensions are from Herman Miller's Aeron dimension drawings for the fully adjustable arms specification. Sizing is from Herman Miller's Aeron size and fit reference, June 2026; weight ratings are Chair Dinkum's stated maximums for the Aeron we sell.
What the measurements mean in practice
Choosing the right Aeron size ensures proper lumbar support and seat depth for your frame
Seat depth. The Aeron does not have an adjustable seat slider. The depth is a single fixed figure per size: 406 mm for A, 432 mm for B, and 470 mm for C. The correct depth means the front edge of the seat sits about two finger-widths behind your knees when your back is fully against the backrest. If the seat is too deep, it will press into the back of your knees. This is the measurement that cannot be adjusted away afterwards, and it is the main reason size matters on an Aeron more than on a chair with a sliding pan.
Width. Overall width is a range rather than a single number, because the arms adjust in and out, and the figure usually quoted is the narrowest setting. Size A runs 698 to 744 mm, Size B 719 to 772 mm and Size C 719 to 803 mm. The three sizes start close together and separate as the arms go out: at full extension a Size C is 31 mm wider than a Size B and 59 mm wider than a Size A. If you are fitting chairs into a tight bench layout, measure at the wide end, not the narrow one.
Seat height. Size A adjusts from 366 to 490 mm, Size B from 376 to 579 mm, and Size C from 401 to 579 mm. The Aeron tops out at 579 mm, so it is a seated-height task chair and cannot be used at a standing desk. If you need to work at a raised surface, the chair to look at is the HÅG Capisco 8106 on the high gas lift.
Arm height. 190 to 292 mm on all three sizes. The arms are the one dimension that does not change with the size you choose.
Back support. Herman Miller lists four back supports for the Aeron — Basic Back Support, PostureFit, Adjustable Lumbar Support and Adjustable PostureFit SL — with the last three listed as options. PostureFit SL uses two independently flexing pads, the top supporting the lumbar region and the bottom stabilising the sacrum. Every Aeron Chair Dinkum holds is the PostureFit SL specification. Our guide to PostureFit SL versus the adjustable lumbar pad explains the difference. If you would rather have the plain lumbar pad, tell us.
Deciding between the Aeron and something else entirely? Our Aeron vs Cosm vs Embody comparison and Herman Miller vs HÅG put the published measurements side by side. This page is about getting the Aeron size right.
Guidance for different workspace types
Home office
For a dedicated home office you can size the chair exactly to one person, which is the easiest case. Find your height and weight on the chart, and if you land in a shared region take the B. Measure your current chair's seat depth and compare it to the figures above — that one comparison tells you more than any amount of reading. Pairing your Aeron with a good monitor arm such as the CBS Flo Single Monitor Arm finishes the setup.
Executive office
If you are buying for a specific person, size it to them on the chart rather than to the room. A Size C Aeron in Onyx with a polished base makes a commanding executive chair, but only specify a C if the chart puts them in one — a tall, lightly built executive is a Size B. Alternatively, explore our range of executive chairs.
Commercial workplace
Where desks are shared or staff change frequently, standardise on Size B. It is the only size that covers the full height range, and it is the one Herman Miller nominates for anyone in a shared region. For larger orders, a core of Size B with a proportion of A and C covers the widest spread of body types while keeping procurement simple. Ring 02 9640 0642 with your headcount and we will work out the ratio with you.
Frequently asked questions
How does Herman Miller decide which Aeron size fits me?
By height and weight together, not height alone. Herman Miller publishes a size and fit chart running from 142 cm to 200 cm and from 41 kg to 181 kg, and you find the point where your height and your weight intersect. Two people of the same height can take different sizes.
Is Size C for tall people?
Not by itself. On Herman Miller's chart Size C is driven more by weight than by height. Someone 180 cm tall and lightly built takes a Size B, while someone of average height and a heavier build can land in a Size C. Check both figures rather than assuming height decides it.
Who is Size A actually for?
It is a narrow specification. On Herman Miller's chart Size A applies between 142 and 155 cm and between 41 and 54 kg. Outside that, even a short user moves into the A-or-B region or straight to Size B.
What if I fall in an "A or B" or "B or C" region?
Take the Size B. Herman Miller's size and fit reference says the B-size chair is designed to fit a broad range of people and recommends it for users who fall in the A/B or B/C category.
How do I know what size my current Aeron is?
Feel the back of the chair. Run your fingers underneath the top edge of the backrest frame, directly behind the Herman Miller logo. You will feel small raised bumps: one bump means Size A, two bumps mean Size B, and three bumps mean Size C.
Can I adjust the seat depth on an Aeron?
No. Unlike many ergonomic chairs that feature a sliding seat pan, the Aeron's seat depth is fixed at a single measurement per size: 406 mm for Size A, 432 mm for Size B and 470 mm for Size C. This is why choosing the correct size matters so much.
Is a Size C wider than a Size B?
At its narrowest, no. Both start at 719 mm. The difference shows up as the arms go out: a Size B reaches 772 mm and a Size C reaches 803 mm, so a Size C is 31 mm wider at full extension. If you are fitting chairs into a tight bench layout, measure at the wide end rather than the narrow one.
What are the weight ratings for each size?
Chair Dinkum states a maximum user weight of 136 kg for Size A and 159 kg for Sizes B and C. These are ratings rather than selection brackets — use the size and fit chart to choose the size, and treat the rating as the ceiling that size is built to.
What happens if I buy an Aeron that is the wrong size?
Too large and the front edge of the seat frame presses into the back of your knees and the armrests sit too far apart, so you splay your elbows to type. Too small and your hips feel pinched between the armrests, the seat does not support enough of your thigh length, and the backrest does not reach high enough to support your upper back.
Ready to find your Aeron
We carry genuine Herman Miller Aeron chairs in six colourways, all with PostureFit SL support and fully adjustable arms. Size A is the one we hold in the smallest numbers at any given moment, so ring us rather than assuming there is one on the shelf.
If you are unsure which size is right, contact our Sydney team on 02 9640 0642, or come and sit in all three at our Pyrmont showroom. Sizes A, B and C are set up side by side, which is the only reliable way to settle it.
References
- Herman Miller, Size/Fit Reference — Aeron Chair, June 2026
- Herman Miller, Aeron Chair dimension drawings, fully adjustable arms, sizes A, B and C
- Chair Dinkum range and stock, checked 21 September 2026
