The Herman Miller Aeron comes in three sizes: A (small) suits roughly 142–163 cm and up to 136 kg, B (medium) suits 158–183 cm and up to 159 kg, and C (large) suits 178–200 cm and up to 159 kg.
If you land in an overlap zone, Herman Miller's own guidance says pick B — but a sit-test beats any chart. Here's how to get it right the first time.
Aeron size chart in cm and kg
Most Aeron size guides are written for the US market in feet and pounds, which is useless when you think in centimetres. Here is the full metric picture, converted from Herman Miller's official specifications and its Size/Fit Reference chart.
| Spec | Size A (small) | Size B (medium) | Size C (large) |
|---|---|---|---|
| Recommended user height | 142–163 cm | 158–183 cm | 178–200 cm |
| Weight capacity (tested & warranted) | 136 kg | 159 kg | 159 kg |
| Seat depth | 40.6 cm | 43.2 cm | 47.0 cm |
| Seat height range | 36.6–49.0 cm | 37.6–57.9 cm | 40.1–57.9 cm |
| Overall width | 69.9 cm | 71.9 cm | 71.9 cm |
| Overall height | 87.0–97.8 cm | 93.3–104.5 cm | 101.6–115.3 cm |
| Size dots under the backrest | 1 dot | 2 dots | 3 dots (triangle) |
Two things to note before you read anything into those capacities: B and C share the same 159 kg rating, so sizing up to a C doesn't buy you any extra weight capacity — it only changes the geometry. And if you're over 136 kg, size A is simply off the table regardless of your height.
What actually changes between A, B and C
All three sizes get the same suspension mesh, the same adjustments and the same tilt quality — you're not buying a "better" chair by going bigger. What changes is the geometry: backrest height, seat width, seat depth and base diameter all scale up as you move from A to C.
The single most important number in that table is seat depth: 40.6 cm on the A, 43.2 cm on the B, 47.0 cm on the C. Unlike many chairs, the Aeron's seat depth is not adjustable, so the distance from the backrest to the front edge of the seat is fixed by the size you choose. The fit test is simple: sitting all the way back, you want at least a couple of fingers' width of clearance between the back of your knee and the front edge of the seat. Too little gap and the seat edge digs into your calves; too much and your thighs lose support and the lumbar area sits in the wrong spot.
Height-wise, the C stands roughly 15–18 cm taller overall than the A, and its minimum seat height starts about 3.5 cm higher — worth knowing if you're tall but your desk is low.
What size Aeron am I? Real-world scenarios
The chart gets most people to the right answer, but the overlap zones (158–163 cm and 178–183 cm) are where buyers agonise. Here's how the common cases tend to play out, based on the official fit reference and the patterns we see when people sit-test all three sizes in our showrooms:
- Around 180 cm, average build: this is the classic "B or C" dilemma. Most people this height land on B — it holds you more snugly and encourages upright posture, and 183 cm owners commonly run a B happily for years. In a C, some 180 cm sitters find the deeper 47 cm seat pan touches the back of the knees and pushes them into a slouch.
- 178–183 cm with long legs, broad shoulders or a heavier build: lean C. The extra 3.8 cm of seat depth and taller backrest are exactly what this frame needs. If a B's backrest edge sits at your shoulder blades rather than clearing them, that's a strong signal to size up.
- Over 183 cm: C, almost always. This is where "the chart said B" complaints come from — tall, lighter-built buyers can chart into B on weight, then find the backrest too short.
- Under 160 cm: take the A seriously. It sits lower (down to 36.6 cm seat height), the shorter 40.6 cm seat depth means your feet actually reach the floor, and the narrower frame fits smaller shoulders. A B can work at the top of the overlap, but petite users often perch forward in one.
- Genuinely between sizes: Herman Miller's official recommendation is to choose B, because it's designed to fit the broadest range of people. It's the default for a reason.
One more nuance: your size can change. Owners report a B that fit fine starting to press into the thighs after weight gain, and muscular or cyclist thighs can push you up a size even if your height says otherwise. If you're near a boundary and your weight fluctuates, size up.
Aeron size dots: identifying an existing chair
Buying second-hand, or trying to work out what you already sit on? Every Aeron carries a built-in answer. Run your fingertip under the top edge of the back frame, directly opposite the Herman Miller logo, and feel for small raised braille-like bumps:
- 1 dot = Size A
- 2 dots = Size B
- 3 dots = Size C — arranged in a small triangle
You'll usually feel them before you see them. Older Classic Aerons that predate the dots can be identified from the label under the seat, where the model number encodes the size. Given how many pre-owned Aerons circulate in Australia, this five-second check is worth doing before you hand over money — and while you're under there, an intact Herman Miller label and model number is also your first authenticity check.
When the chart is wrong: three physical tests
Herman Miller's own Size/Fit Reference is explicit that the chart exists for situations where you can't sit in all three sizes — the sit-test is the definitive method. If you can get into a chair, run these three checks:
- Knee gap: sit fully back. You need roughly two fingers' clearance (up to four is fine) between the seat edge and the back of your knee. Seat edge touching your knee? Size down. A hand's width of gap? You could go up.
- Shoulder-blade clearance: the top of the backrest frame should clear the bottom of your shoulder blades. If the hard frame edge lands mid-blade when you recline, the chair is too small for your torso.
- Thigh-rim pressure: the Aeron's mesh is tensioned inside a firm frame. Check that the side and front rim isn't pressing into your outer thighs — a known irritation point for muscular or broader-thighed sitters, and the most common reason to size up independent of height.
Honest downsides to know before you choose
We sell a lot of Aerons, and we'd rather you buy the right chair than just a chair. The fixed seat depth is the Aeron's biggest sizing limitation — there's no slider to fine-tune fit, which is exactly why the three-size system exists and why the gap between B and C feels large to some bodies. A vocal minority of owners genuinely wish a "B-and-a-half" existed. The firm frame rim can cause thigh pressure for some builds in any size. And no Aeron ships with a headrest — if you want one, the genuine Atlas headrest (AUD $299) is a separate add-on, available in Graphite, Mineral and Onyx to match your chair's finish.
Aeron sizes and prices in Australia
At Aussie Chair, the Herman Miller Aeron runs AUD $1,759–$2,364 depending on size (A, B or C), finish (Graphite, Mineral or Onyx) and base (plastic or aluminium). Every Aeron we sell includes the standard 1-year warranty, with an optional 12-Year Warranty Upgrade for +$220 — a tick-box on the product page. You can browse the rest of our Herman Miller range if you're weighing the Aeron against its siblings.
| Item | Price (AUD) |
|---|---|
| Herman Miller Aeron (sizes A/B/C, Graphite/Mineral/Onyx, plastic or aluminium base) | $1,759–$2,364 |
| 12-Year Warranty Upgrade (optional, product-page tick-box) | +$220 |
| Aeron Genuine Atlas Headrest | $299 |
FAQ
What size Aeron am I?
Match your height first: 142–163 cm suggests A, 158–183 cm suggests B, 178–200 cm suggests C. Then check weight — A is warranted to 136 kg, B and C to 159 kg. In an overlap zone, Herman Miller recommends B, but a sit-test is the only definitive answer.
How do I know if my Aeron is size A, B or C?
Feel under the top edge of the back frame, opposite the Herman Miller logo, for raised dots: one dot is A, two dots is B, three dots in a triangle is C. Older Classic models without dots can be identified from the model number on the label under the seat.
Should I get an Aeron size B or C?
At 178–183 cm you fit both. Choose B if you want a snug fit that keeps you upright — it suits most people in this range. Choose C if you have long legs, broad shoulders or a heavier build, but confirm the deeper seat leaves two fingers' clearance behind your knees.
What size Aeron for someone 180 cm tall?
180 cm sits inside both the B and C ranges. Most 180 cm sitters of average build end up in a B; the C's 47 cm seat depth can press behind the knees and encourage slouching unless you have longer legs or a broader frame.
What is the weight limit of an Aeron chair by size?
The A size is tested and warranted to 136 kg. The B and C sizes are both warranted to 159 kg — sizing up from B to C changes the chair's dimensions, not its weight rating.
Can I try all three Aeron sizes before buying?
Yes. Herman Miller itself treats sit-testing as the primary sizing method and the chart as a fallback. Both Aussie Chair showrooms keep Aerons on the floor so you can run the knee-gap, shoulder-blade and thigh-rim tests in person before choosing.
The chart gets you close; your body makes the final call. Come sit-test the Aeron at our Sydney showroom (Unit 11, 46-50 Wellington Rd, South Granville NSW) or our Melbourne showroom (Shop 1a/280 Whitehorse Rd, Nunawading VIC) — details and hours here — and we'll fit you to the right size in ten minutes. Already know your letter? Order the Aeron online with delivery across Australia and New Zealand.