Generally, knowing how to measure inseam for bike is imperative in getting a bike that fits. That’s more important when buying a kids’ bike or BMX, and that’s where this simple guide comes in.
To measure the inseam, you need to stand straight, preferably against the wall, with your shoes off. Then, place a hardcover book at the crotch and measure the floor-to-book (crotch) distance.
You may repeat the above process thrice and get an average measurement, representing the most accurate inseam height.
Remember, getting the right bike size means riding comfort, better performance, and injury prevention. Also, your height alone is not ideal for getting a 100% perfectly right bike frame, and that’s where the inseam height comes in handy.
This guide will help you know the steps for measuring the inseam length to get the right bike frame. But first, let’s understand what inseam length is below.
What Is Inseam Length?
Inseam length is typically the ‘measurement of your inside leg.’ It is the distance between the floor and the crotch area. Getting it right means having a good bike fit, which translates to comfortability and a good biking experience.
How to Measure Inseam for Bike
Before we can look at the steps, below are a few things that you will require:
Requirements
- Tape measure
- Marker (it can be a masking tape, a pencil, or a pen)
- Hardcover book (one with a rigid spine)
The Steps:
Here’s how to measure a child’s inseam for a bike:
Step 1 – Find a good spot
Generally, you can take your inseam measurements anywhere. However, you should find a perfect spot. One thing to consider is getting a place you can stand straight. It could be next to a closed door or a wall.
Step 3 – Remove your shoes
Let me start by noting that you can measure inseam for a bike without or with your shoes on. But, given that you are likely to ride your bike with your riding shoes, it’s advisable to measure your inseam barefoot or with a pair of socks.
That will give you more accurate results, unlike when shoes are on.
Step 4 – Stand up straight
Stand on an even floor with your back straight against the wall and your legs 6 – 8 inches apart.
Step 5 – Place the book at the crotch
Now, get a hardcover book, place it between the legs and adjust it until it touches the crotch. When doing this, ensure that you are still standing straight. You can get help from a friend.
Step 6 – Measure your inseam
In this last part, you should take a tape measure and measure the distance between the floor to the hardcover book (crotch). Mark the length with a marker, pencil, masking tape, or pen.
Remember to do this at least three times, then sum the three values and find their average to ensure you get more accurate results. Overall, all you need to do is get your child to cooperate with you for more accuracy.
How to Determine Your Bike Frame Size using Inseam?
Now that you already know your inseam length, you can go ahead and determine your frame size depending on the bike you want to buy, as shown in the table below:
| Bike Type | Frame Size |
| Road bike | Inseam x 0.70 |
| Mountain bike | Inseam x 0.66 |
| Trekking bike | Inseam x 0.64 |
| Hybrid/Cruiser/City bike | Inseam x 0.665 |
So, if you want to get a hybrid bike frame, and your inseam is 80cm, your perfect frame fit would be:
80 cm x 0.665 = 53 cm
That means a hybrid bike with a frame size of 53cm will fit you perfectly. You can use the same formula on any other bike that you want to order.
To give you an in-depth frame size according to your inseam, let’s look at various bike size chart by height and inseam below. Also, you can consider this recent article I did on bike frame size chart:
Road Bike Frame Size by Inseam and Height
Here’s a table to match your inseam and rider height with the right road bike frame.
| Frame Size Name | Frame Size | Rider’s Inseam | Rider’s Height |
| XX-small | 33 – 37cm | 60.9 – 73.6cm | 4’10” – 5’2″ |
| X-small | 38 – 42cm | 63.5 – 76.2cm | 5’2″ – 5’6″ |
| Small | 43 – 47cm | 66 – 78.7cm | 5’6″ – 5’10” |
| Medium | 48 – 52cm | 68.6 – 81.3cm | 5’10’’ – 6’1’’ |
| Large | 53 – 57cm | 71.1 – 83.8cm | 6’1″ – 6’4″ |
| X-large | 58 – 61cm | 73.6 – 86.4cm | 6’4’’ –6’6’’ |
Mountain Bike Frame Size by Inseam and Height
Consider this table to match your inseam and height with the correct MTB bike frame.
| Frame Name | Frame Size | Rider’s Inseam | Rider’s Height |
| XX-small | 13 – 14″ | 60.9 – 73.6cm | 4’10” – 5’2″ |
| X-small | 15 – 16″ | 63.5 – 76.2cm | 5’2″ – 5’6″ |
| Small | 17 – 18″ | 66 – 78.7cm | 5’6″ – 5’10” |
| Medium | 19 – 20″ | 68.6 – 81.3cm | 5’10’’ – 6’1’’ |
| Large | 21 – 22’’ | 71.1 – 83.8cm | 6’1″ – 6’4″ |
| X-large | 23 – 24’’ | 73.6 – 86.4cm | 6’4’’ – 6’6’’ |
Commuter/Hybrid/City Bike Frame Size by inseam and Height
The guide for matching a commuter, hybrid, or city bike frame with the rider’s inseam and height is similar to that of MTBs. So, consider it as follows:
| Frame Name | Frame Size | Rider’s Inseam | Rider’s Height |
| XX-small | 33 – 37cm | 60.9 – 73.6cm | 4’10” – 5’2″ |
| X-small | 38 – 42cm | 63.5 – 76.2cm | 5’2″ – 5’6″ |
| Small | 43 – 47cm | 66 – 78.7cm | 5’6″ – 5’10” |
| Medium | 48 – 52cm | 68.6 – 81.3cm | 5’10’’ – 6’1’’ |
| Large | 53 – 57cm | 71.1 – 83.8cm | 6’1″ – 6’4″ |
| X-large | 58 – 61cm | 73.6 – 86.4cm | 6’4’’ – 6’6’’ |
How to Measure Bike Size for Kid?
Kids’ bikes are not measured like adult bikes. In this case, you need to get your kid’s inseam length and match it with the wheel size, as shown below.
| Wheel Size | Inseam Length (in cm and inches) |
| 10-inch | 85 – 90cm (12 – 14″) |
| 12-inch | 35 – 42cm (14 – 17″) |
| 14-inch | 40 – 50cm (16 – 20″) |
| 16-inch | 45 – 55cm (18 –22″) |
| 18-inch | 50 – 60cm (20 – 24″) |
| 20-inch | 55 – 63cm (22 – 25″) |
| 24-inch | 60 – 72cm (24 – 28″) |
| 26-inch | 72cm + (28’’+) |
Closing Remarks
There you’ve it – how to measure inseam for bike. As shown above, getting your inseam is easy. You need to stand straight against a closed wall or door, open your legs 6-8 inches apart, place a hardcover book to the crotch and measure the distance from the floor to the crotch.
When you get the inseam length, you can order a bike, and rest assured that it will fit perfectly.