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.
This guide will help you understand the differences between Aeron Size A, Size B, and Size C, and give you clear, practical advice on which size to choose. The Aeron is sized primarily by your height. Weight is a rating ceiling for each size, not a bracket you have to fall inside. Whether you are outfitting a home office or a corporate workspace, getting the size right ensures maximum comfort and ergonomic benefit. 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.
The Herman Miller Aeron Sizing Framework
The Aeron comes in three sizes (A, B, C) to accommodate different body types
Herman Miller designed the Aeron in three sizes to accommodate a much wider range of body types than a standard adjustable chair. The primary differences between the sizes are the seat depth, the seat height range, and the backrest height. This tailored approach is what makes the Herman Miller Aeron one of the most comfortable task chairs available today.
Aeron Size A (Small)
Size A is the most compact version of the Aeron. It is designed specifically for smaller frames and features a narrower seat pan and a shorter backrest. Size A is recommended for people between 147cm and 163cm (4'10" to 5'4") tall, and is warranted for users up to 136 kg. Its seat depth is fixed at 406 mm (16 in) and its overall width is 699 mm. If you find standard office chairs too deep, Size A is an excellent choice.
Aeron Size B (Medium)
Size B is the standard, most popular size, and the size most commonly specified in commercial office fit-outs. If you have ever sat in an Aeron in a corporate office without noticing the size, it was almost certainly a Size B. It is recommended for people between 157cm and 183cm (5'2" to 6'0") tall, and is warranted for users up to 159 kg. Its seat depth is fixed at 432 mm (17 in) and its overall width is 719 mm. This size suits the broadest range of adults.
Aeron Size C (Large)
Size C is built for taller users. It features a deeper seat to support longer legs and a taller backrest to ensure the lumbar support hits the right spot. Size C is recommended for people between 178cm and 198cm (5'10" to 6'6") tall, and is warranted for users up to 181 kg. Its seat depth is fixed at 470 mm (18.5 in) and its overall width is 719 mm, the same overall width as Size B.
Aeron Size Comparison Table
| Specification | Size A (Small) | Size B (Medium) | Size C (Large) |
|---|---|---|---|
| Recommended Height | 147 to 163 cm | 157 to 183 cm | 178 to 198 cm |
| 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 | 699 mm | 719 mm | 719 mm |
| Overall Height | 869 to 978 mm | 935 to 1044 mm | 1016 to 1153 mm |
| Warranted User Weight | 136 kg | 159 kg | 181 kg |
Dimensions are Herman Miller's published Aeron figures. Warranted user weight is published in Herman Miller's Aeron size and fit reference rather than on the public specifications page, which does not list a weight capacity.
How to Choose the Right Aeron Size
Choosing the right Aeron size ensures proper lumbar support and seat depth for your frame
Start with your height, then check that the size you land on is rated for your weight. Here is a simple framework to guide your decision.
Choose Size A if:
- You are between 147cm and 163cm tall.
- You have a petite build and find that standard office chairs are always too deep, meaning the front edge presses into the back of your knees.
- You need the armrests to come in closer to your body for comfortable typing.
Choose Size B if:
- You are between 157cm and 183cm tall with an average build.
- You are buying chairs for a commercial office fit-out where multiple people will share the seating. Size B is the universal standard.
- You are unsure of your size. Size B suits the broadest range of adults.
Choose Size C if:
- You are between 178cm and 198cm tall.
- You need the tallest back and the highest overall height, 1016 to 1153 mm.
- You have long legs and need a deeper seat pan to support your thighs.
What if You Sit Between Sizes?
The recommended height ranges overlap by design, creating two zones where users could reasonably fit into two different sizes. This is a common scenario when selecting Herman Miller chairs.
The A/B Overlap (157cm to 163cm): Herman Miller recommends Size B for anyone who falls between Size A and Size B. Size B gives you 719 mm of overall width against 699 mm on Size A, a 432 mm seat depth against 406 mm, and a taller back, which most users find more comfortable than being cramped in a Size A.
The B/C Overlap (178cm to 183cm): Herman Miller recommends Size B here as well. Both sizes share the same 719 mm overall width, so the real difference is the fixed seat depth: 432 mm on Size B against 470 mm on Size C. Size C is the exception rather than the default, for users whose thighs are long enough that a 432 mm seat leaves them unsupported.
Seat Width, Seat Depth, and Back Support Explained
Seat width: This is one of the most important comfort factors. If the armrests are too far apart, your elbows splay outward and your shoulders fatigue. If they are too close, your hips feel pinched. Herman Miller publishes an overall width of 699 mm for Size A and 719 mm for both Size B and Size C, so moving from Size B to Size C gains you seat depth rather than width.
Seat depth: The Aeron does not have an adjustable seat slider. The seat depth is a single fixed figure per size, not a range: 406 mm (16 in) for A, 432 mm (17 in) for B, and 470 mm (18.5 in) 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 and restrict circulation.
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.
Back support: All three sizes are available with the same three back support options: basic zonal support (8Z Pellicle mesh only), adjustable lumbar support, and adjustable PostureFit SL. PostureFit SL supports both the lumbar and sacral regions of the spine. PostureFit SL is the most advanced option and is included on all Chair Dinkum Aeron chairs.
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 choose the exact size that fits your body perfectly. Take the time to measure your current chair's seat depth and compare it to the Aeron specs above. If you work from home full-time, getting the right size is especially important because you will be sitting in this chair for eight or more hours a day. Pairing your Aeron with a high-quality monitor arm like the CBS Flo Single Monitor Arm can further enhance your ergonomic setup.
Executive Office
If you are buying a chair for a specific executive, size it exactly to their dimensions. A Size C Aeron in Onyx with a polished base makes a commanding executive chair, provided the user is tall enough to fit it properly. For executives who are between sizes, Herman Miller recommends Size B. Alternatively, explore our range of executive chairs for other premium options.
Commercial Workplace
If you are outfitting an office where desks are shared or employees change frequently, standardise on Size B. It is the most versatile option. For larger orders, a mix that includes a proportion of Size A and Size C alongside a Size B core covers the widest range of body types while keeping procurement simple. Our team can help you set the ratio for your headcount.
Frequently Asked Questions
How do I know what size my current Aeron is?
If you already have an Aeron and want to know its size, 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 is so important. The seat depth determines how well the chair supports your thighs without pressing into the back of your knees.
Is there a difference in weight capacity between the sizes?
Yes. Size A is warranted for users up to 136 kg, Size B up to 159 kg, and Size C up to 181 kg. These figures are published in Herman Miller's Aeron size and fit reference, not on the public specifications page. They are ceilings rather than recommended bands, so choose your size by height first and use the warranted weight only as a limit.
What happens if I buy an Aeron that is too big?
If you sit in a Size C but have shorter legs, the front edge of the hard plastic seat frame will press into the back of your knees. Additionally, the armrests will be too far apart, forcing you to splay your elbows outward to type. The lumbar support may also sit too high on your back.
What happens if I buy an Aeron that is too small?
If you sit in a Size A but have a larger frame, your hips will feel pinched between the armrests, the seat will not support enough of your thigh length, and the backrest will not reach high enough to support your upper back properly.
Is the Aeron Size B really suitable for most people?
Yes. Size B covers the broadest recommended height range, 157cm to 183cm, and is the standard size used in most commercial office fit-outs worldwide. If you fall inside that band with an average build, Size B will almost certainly be the right choice.
Ready to Find Your Perfect Aeron?
Choosing the right Herman Miller Aeron size ensures you get the maximum ergonomic benefit from one of the world's best office chairs. Whether you need the compact support of a Size A, the universal fit of a Size B, or the generous proportions of a Size C, Chair Dinkum has you covered.
We carry a full range of genuine Herman Miller Aeron chairs in six colourways, all with PostureFit SL support and fully adjustable arms. Investing in the right chair is an investment in your health and productivity.
Shop Herman Miller Aeron Chairs
If you are still unsure which size is right for you, contact our Sydney team for expert advice, or visit our showroom to test sit the different sizes before you commit. Because a chair this good deserves to fit perfectly.
