Finding your size on a BMC gravel bike
BMC runs two gravel bikes that sit at opposite ends of the sport. The URS is the exploration bike, with long, tall, slack geometry built for rough and technical terrain. The Kaius is the race bike, low and road like, meant for speed on hardpack and pavement. That difference is the single most important thing to grasp, because the two are sized on different conventions: the URS uses letter sizes, the Kaius uses numeric sizes like a road bike. On gravel, reach drives how stretched the cockpit feels, so read height and reach together. You can see what is in stock in the BMC collection.
Please note. These charts are indicative, not a guarantee. Gravel fit depends on proportion, flexibility and the terrain you ride, and two riders of the same height can need different sizes. Use this as a starting point and confirm against the exact bike before buying.
Quick size finder
| Rider height | Leg length (inseam) | URS (adventure) | Kaius (race) |
|---|---|---|---|
| 158–167 cm | 73–78 cm | XS | 47 |
| 166–172 cm | 76–81 cm | S | 51 |
| 172–180 cm | 80–85 cm | M | 54 |
| 178–186 cm | 84–90 cm | L | 56 |
| 184–192 cm | 88–93 cm | L / XL | 58 |
| 190–198 cm | 91–96 cm | XL | 61 |
The URS runs a longer reach than the Kaius at a comparable height because it is designed to be paired with a short stem. Do not be surprised if your URS size feels roomier on paper than your road bike.
How to measure yourself
Height. Stand against a wall without shoes, heels together, and mark the top of your head. Measure straight down to the floor.
Leg length (inseam). With your back to the wall, place a hardback book spine up between your legs and pull it firmly against your body, as a saddle would sit. Mark the top edge on the wall and measure down to the floor. Inseam guides standover clearance, which is especially useful on the URS where you may put a foot down on technical ground.
URS
The adventure platform. Long front centre, tall stack and a slack head angle make it stable and confident on rough tracks, and it is designed around a short stem. Tyre clearance is generous. Note that the XS and S share the same 560 mm stack and differ only in reach.
| Size | Stack (mm) | Reach (mm) | Rider height |
|---|---|---|---|
| XS | 560 | 390 | under 167 cm |
| S | 560 | 400 | 165–170 cm |
| M | 580 | 410 | 168–178 cm |
| L | 610 | 420 | 176–188 cm |
| XL | 640 | 430 | over 188 cm |
Fit character: a stable, confident adventure fit for rough and technical gravel, run with a short stem.
The URS 01 LT shares this exact frame geometry but adds a short travel suspension fork, so the numbers above apply to both. Under rider weight the suspension fork settles slightly, which lowers and shortens the front end a touch in real use.
Kaius
The race gravel bike, with geometry and tube shapes shared with BMC's road racer. Low and long, stiff and fast, it favours speed over all day comfort and reads much more like a road bike than the URS.
| Size | Stack (mm) | Reach (mm) | Rider height |
|---|---|---|---|
| 47 | 521 | 385 | under 166 cm |
| 51 | 541 | 392 | 166–174 cm |
| 54 | 561 | 396 | 172–180 cm |
| 56 | 581 | 400 | 178–186 cm |
| 58 | 606 | 405 | 184–192 cm |
| 61 | 631 | 409 | over 190 cm |
Fit character: a low, long race gravel position for riders who want road bike speed off the tarmac.
What BMC riders find
The URS is described as confidence inspiring and stable, agile when pushed yet calm at cruising pace, with the compliant frame and short travel elements smoothing rough tracks. Riders treat it as the drop bar option that behaves almost like a hardtail on technical ground. The Kaius earns the opposite reputation: fast, stiff and road like, quicker and more responsive on hardpack than adventure gravel bikes, but less relaxed. Some testers note the aggressive position and narrow stock bars can feel twitchy in slow, steep, technical corners.
Between two sizes?
If your height sits between two rows, decide by terrain and position. On the URS, size down for a nimbler, more playful feel or up for extra stability on fast, rough ground. On the Kaius, size down for a racier, more aggressive fit or up for a slightly taller, more comfortable front end. Standover clearance matters more on the URS, so factor in your inseam and share it with us if you are unsure.
Shop BMC at Bikeroom
Browse the current range in the BMC collection, where each listing shows the exact frame size in stock.
Not sure whether the URS or the Kaius suits you, or which size to pick? Send us your height, inseam and current bike fit and we will match you from current stock. Talk to our concierge.
Stack and reach figures are official where available, drawn from published BMC geometry for the current generation URS and Kaius. URS rider height bands come from BMC's own overlapping chart, and the Kaius per size height bands are approximate pending confirmation against BMC's official size chart. Always confirm the geometry and size of the exact bike before you buy.
