Bike Size Chart: Adult Frame Sizes by Height and Inseam
For adults buying a road, mountain, hybrid, gravel or BMX bike: the frame size for your height, how to confirm it with your inseam, and the adjustments that fine-tune the fit once you own it.
Pick a frame from your height, then confirm it with your inseam. A rider 5 ft 7 in to 5 ft 10 in (170 to 178 cm) usually fits a 53 to 55 cm road or gravel bike, or a medium mountain or hybrid bike (17 to 18 in). Each step of about 3 in (7 to 8 cm) in height moves you one size up or down.
- Road, 5'7"–5'10"
- 53–55 cm
- MTB, 5'7"–5'10"
- Medium, 17–18 in
- Road frame formula
- inseam × 0.67
- Saddle height
- inseam × 0.883
On this page
Road bike size chart
Road frames are sold in centimeters, traditionally the length of the seat tube. Modern sloping frames make that measurement less meaningful, so many brands now use XS to XL letters with a centimeter "equivalent". The chart shows where most brands put each size.
| Rider height | Height (cm) | Frame size (cm) | Letter size |
|---|---|---|---|
| 4 ft 10 in – 5 ft 1 in | 148–155 | 47–49 | XXS–XS |
| 5 ft 1 in – 5 ft 4 in | 155–163 | 49–51 | XS–S |
| 5 ft 4 in – 5 ft 7 in | 163–170 | 51–53 | S |
| 5 ft 7 in – 5 ft 10 in | 170–178 | 53–55 | M |
| 5 ft 10 in – 6 ft 1 in | 178–185 | 55–57 | L |
| 6 ft 1 in – 6 ft 4 in | 185–193 | 57–60 | XL |
| 6 ft 4 in and taller | 193+ | 60–63 | XXL |
Race bikes have a lower, longer front end than endurance bikes of the same size. If you are close to the boundary and want an upright position, the endurance model in the smaller size often fits better than the race model in the larger one.
Mountain bike size chart
Mountain bikes are listed by letter and, on many brands, by a seat tube length in inches. Since about 2015, seat tubes have shortened to make room for dropper posts, so the inch figure is now a weak guide. Reach (explained below) is the number that separates sizes on current trail bikes.
| Rider height | Height (cm) | Size | Seat tube (in) | Typical trail-bike reach |
|---|---|---|---|---|
| 4 ft 10 in – 5 ft 2 in | 148–158 | XS | 13–14 | 400–425 mm |
| 5 ft 2 in – 5 ft 6 in | 158–168 | S | 15–16 | 420–445 mm |
| 5 ft 6 in – 5 ft 10 in | 168–178 | M | 17–18 | 445–470 mm |
| 5 ft 10 in – 6 ft 1 in | 178–185 | L | 19–20 | 470–495 mm |
| 6 ft 1 in – 6 ft 4 in | 185–193 | XL | 21–22 | 495–520 mm |
| 6 ft 4 in and taller | 193+ | XXL | 23+ | 520 mm+ |
Cross-country bikes run a little shorter in reach than the trail figures above, and enduro bikes a little longer. XS frames often come with 27.5 in wheels while larger sizes use 29 in; the bicycle tire size chart explains the wheel standards.
Hybrid and gravel bike sizes
Hybrids and city bikes follow the mountain bike pattern (inches or S to XL) with a more upright position. Gravel bikes follow the road chart in centimeters but usually have a taller head tube, so the same number feels slightly more upright than a race road bike.
| Rider height | Hybrid size | Hybrid (in) | Gravel size (cm) |
|---|---|---|---|
| 5 ft 0 in – 5 ft 4 in (152–163 cm) | XS–S | 14–15 | 48–51 |
| 5 ft 4 in – 5 ft 7 in (163–170 cm) | S | 15–16 | 51–53 |
| 5 ft 7 in – 5 ft 10 in (170–178 cm) | M | 17–18 | 53–55 |
| 5 ft 10 in – 6 ft 1 in (178–185 cm) | L | 19–20 | 55–57 |
| 6 ft 1 in – 6 ft 4 in (185–193 cm) | XL | 21–22 | 57–60 |
Step-through hybrids have no top tube to straddle, so standover never limits them. That lets a rider between sizes choose freely by reach, and makes them the easiest frames to share between people of different heights.
BMX bike sizes
Almost all BMX bikes have 20 in wheels, so they are sized by top tube length. Freestyle (street and park) bikes use top tubes of 20 to 21.25 in; race bikes have their own size names that start much smaller.
| Rider height | Height (cm) | Top tube |
|---|---|---|
| Under 5 ft 5 in | under 165 | 20–20.5 in |
| 5 ft 5 in – 5 ft 10 in | 165–178 | 20.5–20.75 in |
| 5 ft 10 in – 6 ft 1 in | 178–185 | 20.75–21 in |
| 6 ft 1 in and taller | 185+ | 21–21.25 in or longer |
Race BMX sizes run from Micro Mini and Mini for small children through Junior, Expert, Pro and Pro XL to Pro XXL, with top tubes from about 16 in to about 21.75 in. The names are shared across brands but the exact lengths are not, so use the maker's height range. For children's BMX and other kids' bikes sized by wheel diameter, see the bicycle size guide by age and wheel size.
How to size a bike by inseam
Height charts assume average proportions. Inseam (inside leg length) corrects for long or short legs and is the better guide when you fall between two sizes.
- Measure your inseam. Stand barefoot with your back to a wall, feet about 6 in (15 cm) apart. Pull a hardback book up firmly between your legs, spine up, as a saddle would sit. Mark the top of the spine on the wall and measure from the floor.
- Estimate a road or gravel frame. Multiply inseam in cm by 0.67 for a traditional seat tube measured center to top. An 81 cm (32 in) inseam gives about 54 cm.
- Check standover. Straddle the bike with feet flat. You want about 1 to 2 in (2.5 to 5 cm) between you and the top tube on a road bike, 2 to 4 in (5 to 10 cm) on a mountain bike, and 2 to 3 in on a hybrid.
- Check saddle height can be set. Your target saddle height (below) must fall between the seatpost's minimum insertion mark and its lowest position. On mountain bikes with dropper posts, the frame's maximum insertion often decides whether a long-travel post fits.
Trouser leg length is measured to the crotch seam of the trousers and is typically 1 to 3 in shorter than a cycling inseam taken with a book. Using your jeans size leads to a frame that is too small.
Stack and reach: comparing sizes between brands
A "54" from one brand and a "54" from another can differ by a full size. Two numbers on the geometry chart solve this, because both are measured from the bottom bracket to the top of the head tube:
- Stack is the vertical distance. More stack means a taller front end and a more upright position.
- Reach is the horizontal distance. More reach means a longer cockpit and a more stretched position.
Mid-size road bikes (54 to 56 cm) typically have a reach of about 375 to 395 mm, with stack from roughly 540 mm on race frames to 590 mm on endurance frames. If you like the fit of your current bike, match its stack and reach within about 10 mm on the new one, then fine-tune with the stem and spacers.
Fit adjustments after you choose a size
The frame sets the range; the contact points set the fit. These are the standard starting points that bike fitters refine.
| Adjustment | Starting point | Range to try |
|---|---|---|
| Saddle height (bottom bracket center to saddle top) | Inseam × 0.883 | ±1 cm, in 2–3 mm steps |
| Knee bend at bottom of pedal stroke | About 25–35° | Too straight: hips rock. Too bent: knee strain at the front. |
| Saddle fore-aft | Knee roughly over the pedal axle with cranks level | Saddle rails allow about 3–4 cm |
| Saddle tilt | Level | A degree or two nose-down if you slide forward |
| Stem length | Road 90–110 mm, MTB 35–50 mm | ±10–20 mm changes reach without a new frame |
| Handlebar width | Road 38–44 cm (shoulder width), MTB 760–800 mm | Cut MTB bars in 5–10 mm steps |
| Crank length | 170–172.5 mm for most adults | 165 mm or shorter for small riders |
For an 81 cm inseam, the 0.883 formula gives a saddle height of 71.5 cm (28.2 in), measured along the seat tube from the center of the crank axle to the top of the saddle. An older rule, from a 1967 study by Hamley and Thomas, sets the distance from saddle top to the pedal axle at the bottom of the stroke to 109% of inseam; it lands within a centimeter or so of the same height. A quick check without a tape: with your heel on the pedal at the bottom of the stroke, your leg should be straight; riding on the ball of the foot then gives the right bend.
Do not raise a stem beyond the fork maker's spacer limit (often 30 to 40 mm on carbon steerers) or pull a seatpost above its minimum insertion line. If you need more than that to fit, the frame is the wrong size.
Signs your bike is the wrong size
- Too small: knees come close to the handlebars when you turn, the seatpost is extended past the minimum insertion mark, and you feel cramped even with a long stem.
- Too large: you cannot straddle the top tube with both feet flat, your arms are locked straight on the hoods or grips, and you need a very short stem (under about 80 mm on a road bike) to reach the bars.
- Neck and shoulder pain on longer rides usually means too much reach or drop for your flexibility. Fit the stem and bar height before blaming the frame.
Once your size is settled, the bicycle dimensions guide gives a bike's overall length and width for storage and racks, the roof rack size guide covers carrying it on a car, and the exercise bike dimensions guide helps if you are adding an indoor bike. Other sports equipment sizes are collected in the sports sizes hub.
Frequently asked questions
What size bike frame for a 17 to 19 inch frame?
A 17 to 19 in frame is a medium to large mountain or hybrid bike. Seventeen to 18 in usually suits riders about 5 ft 7 in to 5 ft 10 in (170 to 178 cm), and 19 in suits about 5 ft 10 in to 6 ft 1 in (178 to 185 cm). Brands measure seat tubes differently, so check the maker's own chart.
Is it better to size up or down between two bike sizes?
Size down if you want a more agile bike or have short arms for your height; a longer stem or seatpost can add reach. Size up if you want stability at speed or have a long torso. Riders with long legs and a short torso usually do better on the smaller frame.
Do women need a different bike size chart?
No. Most brands now sell unisex frames sized by the same height charts. Women's-specific models typically differ in contact points (narrower bars, women's saddle, shorter cranks on small sizes) rather than in frame size.
What size e-bike do I need?
E-bikes use the same frame sizes as the equivalent non-electric bike: an e-MTB follows the mountain bike chart and a commuter e-bike the hybrid chart. Check standover carefully, since a battery in the down tube can make step-over frames easier to mount but heavier to hold upright.
Is bike size measured in inches or centimeters?
Both, depending on the type. Road and gravel frames are usually given in centimeters (for example 54 cm), mountain and hybrid frames in inches (17 in) or letters (M). Neither is the wheel size: a medium 29er has 29 in wheels on roughly a 17 to 18 in frame.