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Bike tire size converter
ISO/ETRTO, French and inch marks to bead seat diameter, width and brand circumference charts.
Bead seat diameters (BSD)
| BSD (mm) | Also called | Notes |
|---|---|---|
| 622 | 700C · 29" · 28" (Europe) | Road, hybrid, 29er MTB. Schwalbe: 28" and 29" share this BSD. |
| 584 | 650B · 27.5" · 26 × 1 1/2 | Gravel / 27.5 MTB. Schwalbe: identical to French 650B. |
| 559 | 26" MTB (decimal) | Most mountain bikes and cruisers with decimal inch widths. |
| 571 | 650C · 26 × 1 · 26 × 1 3/4 | Triathlon / TT / small road; also Schwinn middleweight fractional. |
| 630 | 27" | Older road bikes (not 27.5 / 650B). |
| 635 | 700B · 28 × 1 1/2 | Rod-brake roadsters. |
| 590 | 650A · 26 × 1 3/8 (E.A.3) | English 3-speeds and many utility bikes. |
| 597 | 26 × 1 1/4 · 26 × 1 3/8 (S-6) | Older British sport / Schwinn lightweights. |
| 507 | 24" MTB (decimal) | Juvenile mountain bikes and cruisers. |
| 540 | 24 × 1 3/8 (E-5) · 600A | British juvenile, wheelchairs, some utility. |
| 451 | 20" lightweight · OS20 | Juvenile lightweights, some BMX race / folders / recumbents. |
| 406 | 20" BMX / folding | Most BMX, folders, trailers, some recumbents. |
Also: Tire pressure calculator · Tire clearance lookup · ETRTO · Bead seat diameter · Rim width.
BSD names from Sheldon Brown, Schwalbe, Continental. Outside diameter uses Sheldon Brown's rule (rim radius + tire width). Circumference mm from Garmin, Wahoo, Bryton, each brand's own chart, checked 13 Oct 2026. Estimate uses π × (BSD + 2 × width). Sources: Sheldon Brown; Schwalbe; Continental; Garmin; Wahoo; Bryton.
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