How to: Measure a Mountain Bike Frame Size [Ultimate Guide]
Alex McRae- 5 Min To Read
- 19 Oct, 2023
Ever wonder why some mountain bikes feel too small despite having a small frame? You might think the frame is small enough but feel too big. This is what happens when you don’t know the right mountain biking frame.
How do you measure the mountain bike frame size? All agree that a mountain bike frame is different than a hybrid or road bike frame.
Anyway, What Size Mountain Bike Frame Do I Need?
It is not as difficult to find the right size frame, especially with everything so simple. There are many ways to ensure that you get the perfect mountain bike frame size.
Let’s now get into the details of each method:
1. Inseam Measurement
Measure the inner legs.length from top to bottom.
Stand with your legs apart and then measure from the floor to your crotch.
Once you have taken the measurements, you can decide what type of mountain bike and which trail you want to ride.
To get a downhill mountain biking bike, measure your inseam and subtract 14 inches. Mountain bike measurements are in inches so it is best to measure in inches. You can also measure in centimeters and multiply them by 0.3937 to convert to inches.
Add 13 inches to your mountain bike when you take it cross-country. This will allow you to choose the right size mountain bike frame for you.
The best way to measure your inseam for general mountain bike measurements is to multiply your inseam by 0.66.
Below is a comparison of the dimensions of different bike frames.
| Inseam | Mountain Bike Size in Inches |
|---|---|
| 75 | 15 - 16 |
| 76 | 15 - 16 |
| 77 | 15 - 16 |
| 78 | 16 - 17 |
| 79 | 16 - 17 |
| 80 | 16 - 17 |
| 81 | 17 - 18 |
| 82 | 17 - 18 |
| 83 | 18 - 19 |
| 84 | 18 - 19 |
| 85 | 20 - 21 |
| 86 | 20 - 21 |
| 87 | 20 - 21 |
| 88 | 20 - 21 |
| 89 | 20 - 21 |
| 90 | 22 |
This chart can help you to compare your inseam to the mountain bike frame size. The inseam is actually in cm so you don’t need to convert. If you are riding downhill, the inseam will be on the lower side. Cross-country bikes will have the higher side.
2. Height
To determine the best size mountain bike frame for you, you can also use your height.
How do you measure your height. Standing straight on the ground, preferably barefoot, or with light socks, is the best way to measure your height. Start measuring from the ground to your highest point using a tape measure. The result will tell you your height.
Your height will determine the size of your bike frame. The chart below will help you understand the differences in bike sizes for different heights.
Height Vs. Bike Frame Size Chart
| Height in Inches | Frame Size (Inches) | Frame Size |
|---|---|---|
| 4'10" - 5'1" | 14 and below | XS |
| 5'1" - 5'5" | 15 / 16 | S |
| 5'5" - 5'9" | 16 / 17 | M |
| 5'9" - 6'0" | 17 / 18 | L |
| 6'0" - 6'3" | 18 / 19 | XL |
| 6'1" - 6'6" | 19 | XXL |
The measurements given are only recommendations. Your exact bike size will depend on where you are riding your bike. You will need to choose a bike that is the highest in your height if you are riding cross-country trails, and vice versa if you are riding in the hills.
3. Measuring the Bike Frame Size
What if you haven’t been able to identify the size of the bike? You might also be buying a secondhand bike and the seller doesn’t know the size.
The bike size will always be listed on the new bikes. It is usually located just below the seat, near the seat post. Here’s how to get yours if you don’t have one or don’t know the measurements.
Get a tape measure that is in inches if you can. Next, measure the length of the seat, usually from the bottom of the seat post to where the crank arm holds the bike’s pedals. If you have a cm tape measure, multiply the result by 0.3937 to convert the cm into inches.
The exact size of the bicycle frame will be provided, as the measurement of the bike is determined by the length of the seat post.
Advantages of Getting the Right Mountain Bike Frame
You might be wondering if the frame size is important when buying a mountainbike. You could visit a bike shop and test ride in different sizes to find the best fit.
It’s easy to go to the shop and choose the bike that gives you the best ride. But what if there are several bikes? Every bike is different. Some bikes feel great on the first ride, while others are quite uncomfortable. It is important to know what you want before you make any decisions based on your first impressions.
You may also want to buy a bike online. It is cheaper and more convenient. If you don’t know the best sizes for you, you can’t buy a bike online. Knowing the right size bike frame will help you in this instance.
Why is the bike frame size important? The right size bike frame will keep you comfortable while riding. It protects your crotch from injury. It is also difficult to control a mountain bike in rough off-road conditions if it is very large.
Bottom Line
How do you measure the size of a mountain bike frame? I hope you now have the information you need. It is up to you now to take the measurements of your ideal bike frame to have a more exciting and satisfying ride.
