Will Your Chair Fit You? Four Simple Measurements

Why We Need Your Body Measurements

To ensure you have the right chair for your workstation, we need to understand how your body dimensions relate to chair specifications. These measurements help us confirm whether the chair you already have, or one we recommend, fits your body properly.

During face-to-face assessments, the DSE and ergonomics assessor will take these measurements. For video assessments, you'll need to take them yourself, which is why we've created this guide.

Most people can be comfortably accommodated by standard office chairs, provided they're properly specified and adjusted. The key is matching your body measurements to the chair's adjustment ranges, seat depth, width, backrest height, and weight capacity.

We focus on four essential measurements because good quality modern office chairs are designed with lots of adjustability built in. This means we can usually find suitable options without needing specialist or custom-built chairs. When we do encounter measurements that fall outside typical ranges, that's when we explore custom solutions.

The instructions below will help you take accurate measurements and understand how each one influences chair selection. More importantly, you'll understand why these measurements matter for your comfort and long-term health at work.

Before You Start – Kit, Clothing & Setup

You'll need: A metric tape measure (mm scale) and a firm, level chair; a helper is handy but not essential.

Preparation:

• Wear normal work clothes and remove bulky layers like coats or thick jumpers
• Sit upright on a firm, flat chair (your current office chair, dining chair, or similar works well, avoid sofas)
• Keep both feet flat on the floor with knees at roughly 90°
• Sit with your back fully against the backrest
• Keep the tape measure straight and begin at the metal tip, not the "1 cm" mark

The Four Critical Measurements

1. Back of buttocks to back of knee (seat depth)

How to measure:

1. Place a book or flat object behind your back to create a straight reference surface, you don't have to do this but its helpful
2. Sit with your pelvis pushed back so it touches the book/flat surface
3. Run the tape measure along the top of your thigh from the book or flat surface to the crease behind your knee
4. Keep the tape level and straight
5. Record the distance in mm and repeat once to confirm

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Why we need this: This prevents the seat cutting into the soft tissue behind your knees and ensures proper blood circulation to your legs. Pressure behind the knees can cause circulation problems and discomfort. This measurement is particularly important if you're shorter, as you don't want the seat butting up against the back of your knees.

How we apply it: Your measurement becomes the maximum seat depth needed. The chair should have a seat slide adjustment (typically 50 mm range) so the minimum seat depth is your measurement minus 50 mm. It's better to err on the side of a shorter seat depth than longer, a seat that's too long creates major ergonomic issues. We really don't want to over-measure here, as a seat that's too long is much worse than one that's slightly too short.

2. Seated hip width at widest point (seat width)

How to measure:

1. Place the tape measure across the seat underneath where your thighs will sit
2. Sit down on the tape measure with your thighs fully on the seat (don't perch on the edge)
3. Position your legs naturally apart, as you would normally sit
4. Move the tape measure so it's positioned at the widest point of your hips/thighs
5. Ensure the tape measure is straight across from one outside edge to the other
6. Read the measurement at the outside edge of your thigh
7. Record in mm and repeat to confirm accuracy

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Why we need this: This ensures the seat isn't too tight, which causes pressure points. It also prevents the seat being too wide, which reduces armrest effectiveness.

How we apply it: The chair seat can be up to 20 mm narrower than your measurement because you don't sit on the very outer edges of your thighs. The seat shouldn't be more than 50 mm wider than your measurement. Excessive width in the seat can make the armrests less effective (they'll be too far apart to provide proper support) and can make you feel lost in an oversized chair.

3. Seat surface to shoulder height (backrest height)

How to measure:

1. Ensure your buttocks are fully back against the backrest (same position as measurement 1)
2. Measure vertically from the seat surface to the top of your shoulder
3. Keep your torso upright, don't shrug or slouch
4. Record in mm and take measurement twice for accuracy

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Why we need this: The backrest must support your entire spine and allow the lumbar support to sit in the correct position for your back.

How we apply it: The chair's backrest height doesn't need to reach the full height of your shoulder measurement. The critical support comes from the lumbar region and mid-back. Anywhere from the mid-back up to just below the shoulders is acceptable as long as lumbar support is in the right spot. The top of your shoulders are primarily muscle and don't require the same structural support as your spine.

4. Body weight

How to measure:

1. Weigh yourself on reliable scales
2. Wear normal clothes (not heavy coats)
3. Record in kg
4. An approximate weight is fine, we just need to ensure the chair's capacity is suitable

Why we need this: Chair mechanisms and gas stems are rated by weight for safety and durability. The reason for this measurement is to ensure your chair won't fail under normal use.

How we apply it: We only consider chairs whose tested weight capacity exceeds your weight with a safety margin built in.

Common Measurement Mistakes to Avoid

Watch out for these pitfalls:

• Twisted or angled tape measure
• Starting from the "1cm" mark instead of the metal tip
• Measuring over clothing folds or bulky items
• Recording measurements in cm instead of mm
• Taking measurements while slouching or in poor posture

Why We Don't Ask for Other Measurements

You might wonder why we don't take all the traditional anthropometric measurements. Here's why our simplified approach works:

Back of knee to floor height: Gas stems easily adjust for height differences. We only need to know if you're over 183 cm (6'0") to specify a taller gas stem.

Nape of neck height: Modern headrests adjust ±60 mm, covering normal variation. Combined with your seat-to-shoulder measurement, this covers neck support needs.

Seat to underside of arm: Height-adjustable armrests make this measurement redundant for most people.

Elbow width: This is often measured traditionally, but it's largely determined by the seat width. Since we're already measuring your seat width, this ensures the armrests will be positioned correctly for your body.

Our principle: Modern chair adjustability reduces measurement requirements for the vast majority of employees, keeping the process simple while maintaining accuracy.

Converting Your Measurements to Chair Specifications

Here's how your measurements translate into chair requirements:

Seat depth: Maximum needed = your measurement; minimum acceptable = your measurement minus 50 mm

Seat width: Chair can equal your measurement or be up to 20 mm narrower, but no more than 50 mm wider

Backrest height: Must provide adequate lumbar and mid-back support based on your seat-to-shoulder measurement

Weight capacity: Chair must exceed your weight with safety margin

Why adjustment range matters: We're not looking for a static fit, but a chair that can be fine-tuned to your exact needs through its adjustment mechanisms.

When Standard Chairs Work (And When They Don't)

The vast majority of employees can be comfortably accommodated by adjustable standard chairs. Modern office chairs offer substantial adjustment ranges that cover most body dimensions when properly specified.

When measurements fall outside typical ranges: We'll contact you for one or two additional measurements or arrange a quick video call to discuss specialist options.

The goal: Finding a chair that can be tailored to your body through adjustments rather than requiring custom manufacturing.

Quick Reference: Your Four Numbers

Email these measurements (in mm) as part of your assessment:

1. Back of buttocks to back of knee: ___ mm
2. Seated hip width: ___ mm
3. Seat surface to shoulder: ___ mm
4. Body weight: ___ kg

Getting the Most from Your Chair Setup

Once you have the right chair specified for your measurements, proper adjustment is crucial. The measurements you've taken will help guide the setup process.

For detailed guidance on adjusting your chair once it's specified, see our comprehensive chair adjustment guide.

Key adjustment tips:

• Use your buttock-to-knee measurement to set seat depth with a 2-4 finger gap behind your knee
• Adjust backrest height so lumbar support aligns with your lower back curve
• Set armrest height so your shoulders feel relaxed

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