Find your starting e-bike frame size using your height, inseam, and the type of e-bike you plan to ride. YSM sizes e-road, e-mountain, e-gravel, and hybrid/commuter e-bikes using the fit principles of their underlying bike category.
E-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
E-bike frame sizing is primarily a fit and geometry question — the same question you would ask for a regular bike, applied to the e-bike's underlying category. YSM turns a few practical inputs into a starting frame size, not a single universal number.
Motor wattage and battery capacity do not determine frame size. An e-bike is sized like the regular bike it is based on — the motor and battery add weight and assistance, but the rider still needs to fit the frame. E-bikes do not all share one geometry, so there is no single generic e-bike frame formula.
Category by category
The question "what size e-bike do I need" has a different answer per subtype. YSM routes each e-bike through the fit principles of its underlying category.
E-road sizing generally follows road-bike fit principles. Height, inseam, reach, stack, and the manufacturer's geometry all remain important. Treat the result as a starting centimeter range with an alpha equivalent.
E-MTB sizing follows mountain-bike fit principles using alpha sizes (S, M, L, XL). When a rider falls between two viable sizes, riding style may matter — a smaller valid option may feel more compact and responsive, while a larger valid option may feel more stable. Use cautious judgement and check the model's geometry.
E-gravel sizing follows gravel-bike fit principles. Height and inseam are useful starting measurements, but reach, stack, and the specific model's geometry should be checked before buying.
These commonly prioritize comfort, stability, and a more upright riding position. Geometry still varies by model — not every commuter e-bike shares the same frame geometry, so check the manufacturer's size chart.
Which measurement matters
Both are useful. Height establishes a starting size range for the e-bike's category. Inseam helps evaluate your proportions and standover clearance.
Two riders of the same height can have different leg lengths, so the same height can point to a different best-fit e-bike size. YSM uses height to place you in a band and inseam as a proportionality check.
Frame design
Step-through frames make mounting and dismounting easier, and the reduced top-tube height can make standover less restrictive. That convenience is real — but it does not mean frame size no longer matters.
A step-through frame does not automatically allow a rider to use any frame size. Pick the size the manufacturer recommends for your height and inseam, then confirm standover and reach feel right.
Handling and confidence
The added motor and battery mass does not by itself determine frame size. You still fit the frame the same way you would fit the underlying regular bike. But e-bike weight and handling can make mounting, stopping, low-speed maneuvering, and overall confidence feel different.
That makes a comfortable fit and a manageable standover especially useful on an e-bike — but it does not justify changing frame size outside the manufacturer's suitable range.
A common confusion
No. Wheel size and frame size are separate measurements. Numbers such as 27.5" and 29" refer to the wheel and tire system, not the rider's frame size.
A 29-inch wheel e-bike still comes in small, medium, large, and extra-large frames — the correct frame size is the key sizing variable, not the wheel diameter.
The common scenario
Being between sizes is normal. When two adjacent sizes are both valid for your measurements, YSM shows a primary starting recommendation, a valid alternate, a fit confidence level, and the optional influence of your riding preference.
Whatever the category, check the model-specific manufacturer geometry before you buy. Frame labels are not standardized across brands.
Before you buy
Three measurements in plain language help you confirm a size beyond the label:
How tall the front of the frame and cockpit sit relative to the bottom bracket.
How long the frame feels from the rider toward the front of the bike.
How much clearance you have when standing over the frame.
E-mountain focus
E-MTB is an important YSM category, so it deserves careful coverage. When two adjacent sizes are both valid for a rider, a smaller frame may feel more nimble and compact while a larger frame may feel more stable at speed.
The rider should not size up or down beyond the manufacturer's suitable fit ranges just to create a handling characteristic. Some modern MTB sizing systems explicitly incorporate riding style into sizing decisions, which supports this nuanced approach — but the final choice should stay within the brand's recommended range for your measurements.
Quick how-to
A two-minute measurement that materially improves your e-bike result.
Your starting e-bike size comes from your height, inseam, and the type of e-bike you plan to ride. YSM sizes each e-bike subtype using the fit principles of its underlying bike category — e-road like a road bike, e-mountain like a mountain bike, and so on. Use the calculator above to get a starting frame size.
In most cases, no. E-bike frame sizing generally follows the geometry of the underlying bike category. The motor and battery add weight and assistance, but they do not determine frame size. You fit an e-bike frame the same way you would fit the regular bike it is based on.
Both are useful. Height establishes a starting size range for the e-bike's category, and inseam helps evaluate your proportions and standover clearance. Two riders of the same height can have different leg lengths, so using both gives a more reliable starting size than height alone.
E-MTB sizing follows mountain-bike fit principles using alpha sizes (S, M, L, XL). When you fall between two viable sizes, riding style may matter — a smaller valid option may feel more compact and responsive, while a larger valid option may feel more stable. Stay within the manufacturer's recommended range and check the model's geometry.
Commuter and hybrid e-bikes commonly prioritize comfort, stability, and a more upright riding position. YSM gives an alpha starting size tuned for a more relaxed fit. Geometry still varies by model, so confirm the manufacturer's size chart for the specific e-bike.
A step-through frame makes mounting and dismounting easier and can reduce standover restrictions, but it does not mean frame size no longer matters. Reach, stack, saddle-height range, and cockpit position still need to fit you. Pick the size the manufacturer recommends for your height and inseam.
No. Battery capacity does not determine frame size. You fit the frame based on your body and the e-bike's underlying category, not the size of the battery. A larger battery may add weight and affect handling, but it does not change the frame size you need.
No. Motor wattage does not determine frame size. The motor provides assistance, but the rider still needs to fit the frame. E-bike sizing is a fit and geometry question, not a power question.
No. Wheel size and frame size are separate measurements. A 29-inch e-bike has 29-inch wheels, but it still comes in small, medium, large, and extra-large frames. The correct frame size is the key sizing variable — wheel diameter does not determine rider fit.
When two adjacent sizes are both valid, a smaller frame may feel more nimble and compact while a larger frame may feel more stable at speed. Do not size up or down beyond the manufacturer's suitable fit range just to create a handling characteristic. Some modern MTB sizing systems factor riding style into sizing, which supports a nuanced choice within the recommended range.
Being between sizes is normal. YSM shows a primary starting recommendation, a valid alternate, a fit confidence level, and the optional influence of your riding preference. For e-MTB, a smaller option may feel more responsive and a larger one more stable. For other e-bike categories, prioritize reach, stack, and comfort rather than applying mountain-bike handling language universally.
Yes. Frame labels are not standardized across brands, so a Medium or 56 cm from one manufacturer may not match another's. Before buying, check the manufacturer's e-bike size chart, stack, reach, standover, saddle-height range, and the specific model's geometry table.