by Mountain bikes are sized according to the riders height and inseam size. The sizing is not universal across all manufacturers or even between frame types of the same manufacturer.
Check the manufacturers size chart for the frame you are considering buying first.
What to do if you are between sizes
If you are between sizes on a mountain bike it is worth noting if you are long in torso or in inseam length for sizing up or down.
A long leg to torso ratio will typically mean it is best to size up. The longer stack height of the larger sized bike will give you a more natural position when riding standing up out of the saddle.
Sizing up a frame size with a long inseam ensures that the drop distance from the saddle down to the handle bars is not too long.
For longer torso riders, you can size up or down depending on your preference. To either have a smaller feeling cockpit or a wide and roomy cockpit at front of the bike.
For downhill trail mountain biking we recommend sizing up in most cases as a longer reach will provide more stability.
What parts to swap to help bike fit better
If not sizing up you can always swap the handlebars out for greater rise to accommodate taller riders.
You can also toggle the angle of the handlebars to either shorten on lengthen the distance of handlebar grips in relation to your torso.
Size based on inseam
Sizing based on inseam is to ensure you have enough standover room to clear the top tube of the bike when you dismount.
Sizing based on inseam is useful if you have an average inseam length relative to your height. If you have a longer inseam, standover is less of an issue.
Therefore sizing based on frame will usually give you a more accurate fit.
You can look up the standover on bicycle frame manufacturers geometry charts. From there you can work out if your inseam is long enough to clear the top tube.
Below are sizing charts for some of the most popular mountain bike frames:
Sizing Charts for Trek:
Trek Marlin Size Chart
| Rider Height | Inseam | Frame Size |
|---|---|---|
| 4'9.1"- 5'0.9" | 27.0"- 28.9" | XS |
| 5'1.0"- 5'4.9" | 29.0"- 30.9" | S |
| 5'5.0"- 5'7.9" | 31.0"- 31.9" | M |
| 5'8.0"- 5'10.9" | 32.0"- 33.9" | M/L |
| 5'11.0"- 6'1.9" | 34.0"- 34.9" | L |
| 6'2.0"- 6'4.9" | 35.0"- 35.9" | XL |
| 6'5.0"- 6'8.0" | 36.0"- 38.0" | 2XL |
Trek Roscoe Size Chart
| Rider Height | Inseam | Frame Size |
|---|---|---|
| 4'5.9"- 5'1.0" | 25.2"- 28.7" | XS |
| 5'0.2"- 5'5.6" | 28.3"- 31.1" | S |
| 5'3.4"- 5'7.7" | 29.9"- 31.9" | M |
| 5'5.2"- 5'10.5" | 30.3"- 33.1" | M/L |
| 5'9.7"- 6'2.0" | 32.7"- 34.6" | L |
| 6'1.2"- 6'5.2" | 34.3"- 36.2" | XL |
Sizing Charts for Specialized:
Specialized Rockhopper Size Chart
| Height | Size |
|---|---|
| 6'4"- 6'9" | XXL 29 |
| 6'0"- 6'5" | XL 29 |
| 5'9"- 6'1" | L 29 |
| 5'4"- 5'10" | M 29 |
| 5'4"- 5'10" | M 27.5 |
| 5'0"- 5'5" | S 29 |
| 5'0"- 5'5" | S 27.5 |
| 4'8"- 5'1" | XS 27.5 |
| 4'3"- 4'9" | XXS 26 |
Specialized Fuse Size Chart
| Height | Size |
|---|---|
| 4'10"- 5'1" | XS |
| 5'2"- 5'5" | S |
| 5'5"- 5'10" | M |
| 5'10"- 6'1" | L |
| 6'1"- 6'4" | XL |
Sizing Charts for Giant:
Giant Talon Size Chart
| Height | Frame Size |
|---|---|
| 5’1” - 5’5” | XS (27.5") |
| 5’4” - 5’8” | S (27.5") |
| 5’4” - 5’8” | S (29") |
| 5’7” - 5’10” | M (27.5") |
| 5’7” - 5’10” | M (29") |
| 5’9” - 6’1” | L (29") |
| 6’0” - 6’4” | XL (29") |
Giant Fathom Size Chart
| Height | Frame Size |
|---|---|
| 5’4” - 5’8” | S |
| 5’7” - 5’11” | M |
| 5’10” - 6’2” | L |
| 6’2” - 6’6” | XL |
