Find your starting bike size using your height, inseam, bike type, and riding preference. YSM works with road, mountain, gravel, hybrid/commuter, and e-bikes and helps explain what to do when you fall between sizes.
Bike size calculator
Answer a few quick questions about your height, inseam and bike type to get your starting frame size. The interactive calculator loads here and runs entirely in your browser.
The basics
Bike sizing is influenced by a few practical factors. YSM turns them into a starting frame size for your category — not a single universal number.
Which measurement matters
Both matter. Height provides a useful starting size range for your category. Inseam helps cross-check body proportions and standover considerations.
Two riders of the same height can have different leg lengths, so the same height can point to a different best-fit size. YSM uses height to place you in a band and inseam as a proportionality check — it does not pretend one formula is exact for every body.
Quick how-to
A two-minute measurement that materially improves your result.
Category by category
The question "what size bike should I get?" has a different answer per category. Here is how each one tends to be sized.
Road bikes commonly use centimeter frame ranges, and riding position and reach matter a lot. YSM returns an approximate centimeter size with an alpha equivalent for your height and inseam.
Mountain bikes commonly use alpha sizes (S, M, L, XL). Riders between sizes may prefer a smaller bike for a more compact, responsive feel or a larger bike for a more stable, relaxed feel.
Gravel sizing often resembles road-bike sizing, but geometry and intended use can differ. Treat the result as a starting range and check the brand's geometry for the specific model.
Comfort and upright positioning often matter more than on a road or mountain bike. YSM gives an alpha starting size tuned for a more relaxed commuter fit.
E-bike frame sizing generally follows the geometry of the underlying category. The motor or battery size does not determine frame size. YSM routes each e-bike subtype through its base category: e-road to road, e-mountain to mountain, e-gravel to gravel, e-hybrid to hybrid.
The common scenario
Being between sizes is normal — most categories have overlap bands where two adjacent sizes are both reasonable. YSM shows both candidates and recommends one as a starting point.
YSM uses your measurements and your optional riding preference to provide a starting recommendation. Manufacturer geometry should still be checked before you buy — especially for mountain bikes, where brands overlap sizes intentionally.
Before you buy
A Medium or 56 cm frame from one manufacturer may not match the geometry of another manufacturer's Medium or 56 cm frame. The label is a starting point, not a standard.
Before buying, check the manufacturer's size chart, stack, reach, standover, and the specific model's geometry. YSM is a starting-size advisor — not a replacement for manufacturer geometry.
Bike size is driven mainly by your height and inseam, then refined by the type of bike and how you want it to feel. This calculator places you in a generic size band for your category, cross-checks your inseam proportionality, and tells you when you fall between two sizes. Always confirm against the manufacturer's size chart before buying.
Both. Height establishes the starting size band for your category. Inseam is a cross-check: it tells us whether your legs are proportionate, relatively short, or relatively long for your height, which affects stand-over and reach. Two riders of the same height can need different sizes because of different proportions.
Being between sizes is normal. We show a primary starting size and an alternate. The smaller size is generally more compact and responsive; the larger size is generally more stable and relaxed. Your riding-feel preference helps choose between them, but you should still check the manufacturer's geometry before buying.
There is no universal answer. Modern mountain-bike brands often intentionally allow overlap between sizes. If you want a more nimble, responsive ride, favor the smaller candidate; if you want stability and a relaxed feel, favor the larger candidate. Use the manufacturer's reach and stack numbers to decide.
No. A 56 cm or Medium frame from one manufacturer may not match the geometry of the same labeled size from another. Always verify the manufacturer's size chart, stack, reach, and stand-over for the specific bike you are considering. This calculator is a neutral starting point, not a brand-specific guarantee.
Stand barefoot against a wall with your feet roughly shoulder-width apart. Place a book or similar flat object between your legs, pulled up gently to simulate saddle pressure. Measure from the floor to the top edge of the book. Enter that measurement into YSM in inches or centimeters.
E-bike frame sizing follows the geometry of the underlying bicycle category: e-road bikes use road sizing, e-mountain bikes use mountain sizing, e-gravel bikes use gravel sizing, and e-hybrid or commuter e-bikes use hybrid sizing. Use this calculator with your e-bike subtype selected to get a starting frame size.
Not in terms of frame size. The motor or battery does not determine the frame size — the underlying bicycle geometry does. An e-mountain bike is sized like a mountain bike, and an e-road bike is sized like a road bike. Choose your e-bike subtype in YSM and the sizing logic routes accordingly.
No. A bike size calculator gives a practical starting size based on generic size bands for your category, your height, and your inseam. It cannot account for every brand's geometry or your personal flexibility and riding style. Treat the result as a starting point and verify with the manufacturer's size chart.
Yes, always. Frame labels like Medium or 56 cm are not standardized across brands. Before buying, check the manufacturer's size chart and the specific model's stack, reach, and stand-over measurements against the starting size YSM suggests.