Turn a sit-bone measurement into a precise saddle width in millimetres and see the closest stocked widths from Specialized, Bontrager, Fizik, and other major brands.
Saddle width is the single most important sizing variable for comfort. Your ischial tuberosities — the two bony points at the bottom of your pelvis — are what should support your weight. A saddle too narrow forces that pressure onto soft tissue; a saddle too wide creates inner-thigh chafing.
Start with an accurate sit-bone measurement (the calculator above converts millimetres or inches). Then add padding based on your riding position — more forward rotation means more padding, because the contact region shifts forward as your pelvis tips.
If you want a more nuanced gender- and style-aware calculation, try our saddle size calculator. For full bike fit, combine with saddle height and reach & stack.
| Brand | Stocked widths (mm) | Notes |
|---|---|---|
| Specialized | 143 / 155 / 168 | Ass-o-meter at dealers; Mimic and Power ranges |
| Bontrager | 138 / 145 / 155 / 165 | Four widths — finest granularity among majors |
| Fizik | 140 / 145 / 155 | "Spine concept" shape categories (Bull/Chameleon/Snake) |
| Selle Italia | 135 / 145 / 155 | ID Match system; Lady variants common |
| Ergon | 145 / 155 | Standard + Wide; narrow two-option line |
Picks verified on Amazon — prices and availability may vary.
Fizik
Available widths 142, 154 mm; fits sit-bone 120–145 mm
Selle Italia
Available widths 155, 168 mm; fits sit-bone 130–155 mm
Wtb
Available widths 142, 155 mm; fits sit-bone 130–155 mm
Brooks England
Fixed width 155 mm; fits sit-bone 130–160 mm; requires break-in period (50–100 miles)
Ergon
Available widths 130, 140, 150, 160 mm via sit-bone width measurement; fits sit-bone 110–170 mm
Selle Royal
Available widths 145, 160, 175 mm; fits sit-bone 130–175 mm
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Enter your sit-bone width to see the target saddle width and brand matches.