First, make sure it fits you.

Step 1 — Measure your sit bones

You need a piece of corrugated cardboard and a ruler. That’s it.

1. Put the cardboard on a hard, flat bench or chair — not a padded one.
2. Sit on it for about 30 seconds.
3. Lean forward a little and lift your feet, so more of your weight goes through your sit bones.
4. Stand up. You should see two shallow dents.
5. Measure between the centers of the two dents, in inches. Working in centimeters? Divide by 2.54 — 11.5 cm is 4.5″.

If balancing with your feet up feels unsteady, keep your hands on the seat and skip the lift — the dents will just be fainter. No dents at all? Sit a little longer, or use a softer single-layer piece of cardboard. And it is fine to lift the cardboard onto a table to measure instead of bending down to it.

Most adults land somewhere between 4″ and 6″. For the longer version of this method, see measuring your sit-bone width at home. Cyclist? The same number sizes a saddle — saddle width calculator. There is no “good” or “bad” number — it’s just anatomy.

Step 2 — Check it against the openings

The Socket Seat’s openings sit 6″ apart, center to center (3.5″ wide each, with 2.5″ of foam between them).

Your sit-bone width (inches)

Check fit

Not sure whether your pain is even a sit-bone problem? Tailbone pain and sit-bone pain need opposite cushion shapes — worth two minutes before you buy.

Never sat on a cutout cushion? Seat cushions with cutouts, explained covers the three shapes and who each one fits.

Want to see it rather than read a number? Print the openings at actual size (PDF, one landscape page) and lay your cardboard on top — it carries a ruler so you can confirm your printer did not scale the page.

This is guidance, not a guarantee — how you sit matters as much as the measurement. The 100-day trial is the real test.

What sit-bone width fits the Socket Seat?

The same answer the checker gives, as a table. The range is a performance window, not a bone-contact boundary: inside it, the openings do their job under your sit bones and the bridge of foam stays between them; borderline means you are just past its edge — the people who land there often do well, but we would not promise it.

Fit verdict by sit-bone width

3.6″ to 6.7″	Good fit — inside the range the geometry is designed around
3.3″ to 3.6″ or 6.7″ to 7.0″	Borderline — just past the edge of the designed range; the 100-day trial is built for this case
Under 3.3″	Below the designed range — the geometry will not work as intended for you
Over 7.0″	Above the designed range — the geometry will not work as intended for you

Typical adult sit-bone width runs roughly 4–6″. All of that span lands in the good range — the measurement is how you find out whether you are one of the few people outside it. What the published studies measured.

Step 3 — Check the chair, not just yourself

The geometry can be right for your body and still wrong for your seat. Four things worth checking before you order.

• Seat width You need about 18.5″ of usable width. Chairs with fixed side bolsters — gaming chairs and many car seats — can leave the cushion perched on top of the bolsters instead of settled between them.
• Seat depth At 14.5″ deep it fits most seats. If your seat pan is much shallower, the front edge will overhang — usually fine, occasionally annoying against the backs of your knees.
• Headroom It raises you about 2″. Most drivers find that improves sightlines. In a low-roof car, sit up straight and check you have at least two inches of clearance to spare before you commit.
• Desk height Raising your seat about 2″ changes your relationship to the desk. If your chair is already at its lowest and your elbows are tight to the desktop, factor that in.

None of these are dealbreakers on their own — but they are the four things people tell us they wish they had measured first. Driving in particular has its own constraints — the long-drives page covers headroom, seat shape and vibration.

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Clinicians and ergonomists: a printable patient handout of the measuring method lives on the clinician page.