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Riding a mountain bike that fits properly is a crucial component of getting the most out of your new ride. A proper fit depends on a lot of factors, but getting it right will increase both your comfort and your ability to control the bike when things get rough. You should start by identifying the frame that fits your riding style and dimensions, and then consult a retailer to fine-tune your fit with small adjustments and helpful accessories.

How well a bike fits and feels on the trail is largely determined by its geometry, or the length of a bike’s frame tubes and the angles at which they are put together. The following components of a bike’s geometry will help answer the critical question – what size MTB do I need?

Mountain bike sizing, geometry and fit

Effective top tube

Effective top tube is the horizontal distance from the centre of the head tube to the seat post. This measurement is an important element of how well a mountain bike fits while the rider is seated, and it is influenced by the bike’s seat tube angle and the rider’s saddle height. Riders who spend lots of time in the saddle can focus on effective top tube to determine how a particular bike will handle, and how far they will need to reach to grip the handlebars.


Reach is the horizontal distance from the centre of the head tube to a vertical line that runs perpendicular through the centre of the bottom bracket shell. Reach determines how well a mountain bike fits and how far the rider will need to reach to grip the handlebars while standing. Since trail riders place more emphasis on out-of-the-saddle riding, this measurement is a better indicator than effective top tube as to how their bikes will handle. Reach can be adjusted by swapping the bike’s stem.


Stack is the vertical distance between the centre of the bottom bracket and the horizontal head tube line. This measurement affects the rider’s handlebar height and hand position, so it’s a crucial element of both comfort and control. Luckily, stack can be easily adjusted with headset spacers or simply by raising the handlebar.

Frame size

Trek offers mountain bikes in a range of sizes to accommodate all riders. Mountain bike frame sizes are generally presented in inches, and the chart below can help you to determine which one is best for someone of your height.

Trek provides both 'actual' and 'virtual' frame sizes for its mountain bikes. Actual frame size refers to a measurement of the seat tube from the centre of the bottom bracket to the top of the seat tube. MTB geometry has changed since frames were measured this way – top tubes now generally meet lower on the seat tube to provide a lower stand-over height and more stability – so we coined the term 'virtual frame size'. This refers to the 'traditional' size frame that our bikes actually fit and ride like. The chart below reflects the virtual frame size best for riders of the specified heights.

Mountain - Procaliber, Superfly, X-Caliber, Marlin, Cali Women's, Skye Women's, Stache, Top Fuel, Fuel EX, Lush Women's, Remedy, Powerfly FS

Rider height

148 150 152 154 156 158 160 162 164 166 168 170 172 174 176 178 180 182 184 186 188 190 192 194 196 198
4'10" 4'11" 5' 5'.5" 5'1.5" 5'2" 5'3" 5'4" 5'4.5" 5'5.5" 5'6" 5'7" 5'8" 5'8.5" 5'9.5" 5'10" 5'11" 5'11.5" 6'.5" 6'1" 6'2" 6'3" 6'3.5" 6'4.5" 6'5" 6'6"
13.5 in
15.5 in
17.5 in
18.5 in
19.5 in
21.5 in

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