Backrest Height Adjustment: Why It Matters and How to Set It

Why backrest height matters

The backrest is the primary support surface for your spine while seated. The Occupational Safety and Health Administration (OSHA) states that the backrest should conform to the natural curvature of your spine and provide adequate lumbar support. When the backrest height is wrong, it can push your spine out of its natural alignment or leave parts of your back unsupported.

A backrest that is too low provides no support for the upper back, which encourages slouching and places extra load on the lower spine. A backrest that is too high can press against the shoulder blades or push the shoulders forward, which restricts arm movement and creates tension in the neck and shoulders. Getting the height right is the first step in building a neutral seated posture. Many best office chairs offer backrest height adjustment precisely to address this.

Ergonomics is about designing the work environment to fit the worker, not the other way around. The National Institute for Occupational Safety and Health (NIOSH) describes awkward postures as a risk factor for work-related musculoskeletal disorders. Setting your backrest height correctly is one of the simplest ways to avoid those awkward postures.

How your spine and the backrest interact

Your spine has a natural S-shape when viewed from the side: a slight inward curve in the lower back (lumbar lordosis), an outward curve in the middle back (thoracic kyphosis), and another inward curve in the neck (cervical lordosis). OSHA explains that poor back support can make it more difficult to maintain this natural S-shape of the spine. Understanding lumbar support basics is key to setting the backrest correctly.

The lumbar support of your backrest should fit into the small of your back, filling the gap between your lower spine and the chair. When the lumbar support is positioned correctly, the rest of the backrest can then do its job of supporting the middle and upper back.

Steelcase, in describing its Leap chair, notes that your lower back requires firm, constant support while your upper back requires more support as you recline. This means the backrest height needs to work with both the lumbar region and the upper back, not just one or the other.

How to set the right backrest height

Start by sitting with your back against the backrest. Feel for the lumbar support: it should press gently into the small of your back, around your belt line. If you feel it too high (against your ribs) or too low (on your tailbone), adjust the lumbar height first. For a detailed guide on lumbar depth, see chair backrest lumbar depth.

Next, check the top of the backrest. The ideal position depends on how you work, but a good general target is for the top of the backrest to reach your mid-back or lower shoulder blades. This gives your upper back something to lean against without pressing into your shoulders.

The upper backrest should not push your shoulder blades forward. If you feel pressure on your shoulders that forces them to round, the backrest is too high or angled too far forward. You should be able to reach your keyboard and mouse with relaxed shoulders and elbows close to your body, as OSHA recommends.

OSHA also notes that a backrest should allow you to recline at least 15 degrees from the vertical, with either a lock or tension adjustment to provide resistance to lower back movement. The height and recline adjustments work together: a properly positioned backrest supports your spine through the full range of recline.

The relationship between backrest height and depth

Backrest height is not the only adjustment that matters. OSHA recommends that a backrest have a device that allows it to move forward and backward. This lets shorter users sit with their backs against the backrest without the front edge of the seat pan pressing into their knees, and taller users can keep their buttocks and thighs fully supported.

Some chairs adjust the seat pan position instead of the backrest to achieve this fit. Both approaches can work, but the backrest must be in the right position before you fine-tune the depth or angle. If the backrest sits too far back, you will slump forward to reach your work. If it sits too far forward, it crowds you. Proper seat depth is covered in our chair seat depth guide.

When the backrest height and depth are both set correctly, the lumbar support stays in contact with your lower back through the full range of your sitting postures. This is what OSHA describes as providing adequate support in a variety of seated postures and allowing variability of sitting positions throughout the workday.

Chairs with adjustable backrests

Not all chairs offer independent backrest height adjustment. Some chairs have a one-piece backrest where the lumbar support moves up and down but the overall backrest height is fixed. Others, like the Steelcase Leap, use a contoured back shape that adapts to your spine while still offering a height-adjustable lumbar support.

The Herman Miller Aeron uses a different approach: its PostureFit SL structure supports the sacral and lumbar regions without a traditional padded lumbar pad. The chair is available in three sizes (A, B, and C) designed to fit different body types. This shows that backrest support can come from multiple design strategies, not just a single height adjustment. For a range of options, see our best mesh chairs picks, which often feature adjustable lumbar support.

If you use a chair without adjustable backrest height, OSHA suggests using a rolled-up towel or a removable back support cushion to provide temporary lumbar support. This is a practical stopgap, but a chair with proper adjustments is the longer-term solution.

What to look for in a chair

When shopping for a chair, look for a backrest with at least two useful adjustments: height and angle. The lumbar support should be height-adjustable so you can position it in the small of your back. The backrest should also allow at least 15 degrees of recline with a lock or tension control, as OSHA recommends.

Chairs with a separate or split backrest (sometimes called a two-piece back) give you more control because the lumbar and upper back sections can be positioned independently. A single-piece backrest can work well if the overall height is adjustable and the lumbar support moves independently.

The chair should fit your body size. The Aeron's three sizes (A, B, C) illustrate that different body types need different proportions. A backrest that is proportioned for a different body size will not support your spine correctly, no matter how many adjustments it has. For guidance, see the best office chairs roundup, which compares how different models handle backrest support and other ergonomic features. If you need a chair with a higher weight capacity, our best big and tall chairs guide covers models that still offer full backrest adjustability.

What to pick for your use

Questions

How do I know if my backrest is the right height?

Sit with your back against the backrest. The lumbar support should press into the small of your back (around your belt line), and the top of the backrest should reach at least your mid-back without pushing your shoulders forward. You should be able to reach your keyboard with relaxed shoulders. Many best office chairs have visual guides to help you set this.

What if my chair's backrest is too low?

If the backrest ends below your shoulder blades, you lose upper back support and may slouch. If the chair has adjustable backrest height, raise it. If not, consider adding a lumbar cushion and, when budget allows, replacing the chair with one that offers height adjustment.

Can a backrest be too high?

Yes. If the top of the backrest presses into your shoulder blades or pushes your shoulders forward, it restricts arm movement and can cause tension in your neck and shoulders. Lower the backrest or adjust its angle so it supports your back without crowding your shoulders.

Should the backrest move with me when I recline?

OSHA recommends a backrest that reclines at least 15 degrees from vertical and either locks in place or has tension adjustment. Some chairs also allow the backrest to move forward and backward, which helps maintain contact as you shift positions.

Do I need a separate lumbar adjustment if the backrest height is adjustable?

Not necessarily, but a separate lumbar height adjustment is helpful. Chairs like the Steelcase Leap include a height-adjustable lumbar. Others, like the Herman Miller Aeron, use a differently shaped support structure instead of a separate lumbar pad. What matters is that the support targets your lower back correctly.

Are there differences in backrest support between fabric and mesh chairs?

Mesh backs often have a more flexible frame that contours to your spine, while fabric backs may offer more padding. The adjustment mechanism is similar, but the feel differs. See our best mesh chairs guide for models with adjustable backrests.