Most office chairs are designed for a body between 165 and 185cm tall. If you fall outside that range, or even within it but toward either end, a standard chair may never feel quite right, no matter how many adjustments you make.
This office chair sizing guide for Australia covers the measurements that actually determine fit: seat height, seat depth, backrest height, and weight capacity. It's the practical reference most chair-buying content skips in favour of listing features. Get these numbers right and you'll know exactly what to look for before you buy. Browse the full range of office chairs at EasyMart to compare options once you know your sizing requirements.
Before comparing chairs, it helps to understand what the specifications actually mean and how they translate to your body. These four ergonomic chair dimensions are the ones that matter most.
Seat height is the distance from the floor to the top of the seat cushion. It's the most important dimension for most users because it determines whether your feet can rest flat on the floor and whether your knees sit at or below hip level.
The correct seat height places your feet flat on the floor (or on a footrest), your knees at approximately 90 degrees, and your hips at or slightly above knee level. Most standard chairs offer a seat height range of 40 to 53cm, which suits users roughly between 160 and 190cm tall when paired with a standard desk height of 720 to 730mm.
If the seat is too high, your feet dangle and pressure builds under your thighs. If it's too low, your knees rise above your hips, which tilts the pelvis forward and compresses the lower back. Neither is sustainable for a full workday.
Seat depth is the front-to-back measurement of the seat pan. The correct depth supports the full length of your thighs while leaving a gap of two to three fingers between the front edge of the seat and the back of your knee.
If the seat is too deep, the front edge presses into the back of the knee, restricting circulation and causing discomfort within an hour or two. If it's too shallow, your thighs aren't supported and you'll tend to perch forward, losing the benefit of the backrest entirely.
Standard seat depths run from around 40 to 50cm. Shorter users typically need 38 to 42cm; taller users benefit from 44 to 50cm. Chairs with an adjustable seat slider let you fine-tune this independently of other settings, which is worth prioritising if you're at either end of the height range.
Seat width should allow you to sit comfortably with a small gap on either side, typically 2 to 3cm. Most standard chairs are 45 to 52cm wide, which suits the majority of users. The main concern is that the seat isn't so narrow it creates pressure on the outer thighs, or so wide that the armrests can't be positioned close enough to support the elbows without raising the shoulders.
Backrest height determines how much of your spine the chair supports. A mid-back chair (backrest height of around 45 to 55cm) supports the lumbar region and mid-back. A high-back chair (55cm and above) extends support to the upper back and shoulders, and often includes a headrest.
For users who spend long hours at a desk, a high-back chair with adjustable lumbar support is generally the better choice. The lumbar support should sit at the natural inward curve of your lower back, roughly at the L3 to L4 vertebrae level, which is around 15 to 25cm above the seat surface depending on your torso length.
Shorter users are the most underserved segment in standard office chair design, and the problems are specific and predictable. A chair built for a 175cm user will typically have a seat height minimum of 43 to 45cm, a seat depth of 45 to 48cm, and a backrest that positions the lumbar support too high for a shorter torso. None of these work well for someone 155 to 165cm tall.
What to look for in a petite office chair:
Avoid chairs where the only listed seat height is a single fixed number or a range that starts at 46cm or above. These chairs are not designed for users under 165cm regardless of what the marketing says.
Taller users face the opposite problem: standard chairs often can't go high enough, don't have a deep enough seat pan, and provide a backrest that ends somewhere around the mid-back rather than supporting the full spine.
The consequences are predictable. When the seat is too low, the knees rise above the hips, tilting the pelvis forward and flattening the lumbar curve. When the seat is too shallow, the thighs aren't supported and the user perches forward. When the backrest is too short, the upper back and shoulders get no support at all.
What to look for in a high back office chair for tall people:
The EasyMart Executive Chair range works well here because the extended seat height range and full-length backrest accommodate taller users without requiring a specialist chair.
Weight capacity is listed on most chairs but rarely explained. Most standard office chairs are rated to 100 to 120kg. Heavy-duty chairs extend this to 150kg or more.
The safety implication is obvious, but the performance implication is less discussed. A chair used at or near its weight limit will compress its foam cushioning faster, lose gas lift pressure sooner, and see its mechanism wear more quickly than a chair used well within its rated capacity. For taller or heavier users, choosing a chair rated comfortably above your body weight, not just at it, means the chair maintains its support characteristics over years of use rather than months.
For HR managers buying chairs for a team, specifying a chair with a 130 to 150kg rating as the standard option covers the majority of users comfortably and avoids the need to identify and separately order chairs for heavier team members. To understand how chair choice affects long-term employee comfort, Read our guide on the role of office furniture in employee health and wellbeing.
A well-specified chair still underperforms if it's never adjusted correctly. Most users sit down, raise or lower the seat once, and leave everything else at the factory setting. Here's the correct setup sequence:
| User height | Recommended seat height | Recommended seat depth |
|---|---|---|
| Under 155cm | 38 to 42cm | 38 to 42cm |
| 155 to 165cm | 40 to 45cm | 40 to 44cm |
| 165 to 175cm | 42 to 48cm | 42 to 46cm |
| 175 to 185cm | 45 to 52cm | 44 to 48cm |
| Over 185cm | 50 to 58cm | 46 to 52cm |
These are starting-point ranges. Individual proportions vary, and the two to three finger gap test at the back of the knee is always the more reliable check than a height-based table alone.
Chair fit is personal. A chair that works perfectly for one person can cause real discomfort for another, even at the same desk, doing the same work. The measurements in this guide give you the framework to evaluate any chair against your own body before you buy, rather than discovering the problem after delivery.
Check the seat height range, the seat depth, the backrest height, and the weight capacity. Set the chair up correctly when it arrives. Those two steps alone will determine whether a chair serves you well for years or ends up being replaced within twelve months.
How do I know if my office chair is the right height?|||Sit with your feet flat on the floor and check three things: your knees should be at approximately 90 degrees, your hips should be at or slightly above knee level, and there should be no pressure under your thighs from the seat edge. If your feet are dangling, the chair is too high. If your knees are above your hips, it's too low. Both are correctable with the seat height adjustment, provided the chair's range suits your height.@@@What seat height is right for a 170cm person?|||For a user around 170cm tall, a seat height of 43 to 47cm typically achieves the correct posture at a standard desk height of 720 to 730mm. The precise setting depends on leg length relative to overall height, so use the feet-flat, knees-at-90-degrees test rather than relying on the number alone. If the correct seat height leaves your desk surface too high for comfortable typing, the desk height may also need adjustment.@@@Can I use a footrest instead of adjusting my chair?|||Yes, and for shorter users it's often the correct solution rather than a workaround. If the desk height is fixed and can't be lowered, raising the chair to the correct height for the desk and using a footrest to support the feet is ergonomically sound. The footrest should be angled slightly and large enough to support the full foot, not just the toes.@@@What is seat depth and why does it matter?|||Seat depth is the front-to-back measurement of the seat pan. It matters because a seat that's too deep presses into the back of the knee, restricting blood flow and causing discomfort over time. A seat that's too shallow leaves the thighs unsupported, which causes users to perch forward and lose contact with the backrest. The correct depth leaves a two to three finger gap between the front edge of the seat and the back of your knee when you're sitting fully back against the backrest.@@@Do taller people need a different chair entirely?|||Not always, but they do need to check specific specifications that standard chair listings often don't highlight. The key ones are maximum seat height (should reach at least 53cm), seat depth (should be 45cm or more), and backrest height (should extend to the upper back). Many mid-range chairs marketed as ergonomic are designed for the 165 to 180cm range and won't suit users over 185cm without compromise. It's worth filtering by these specifications rather than relying on general ergonomic claims.@@@
