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How Do You Measure a Bike Frame Effectively? – Guaranteed Ways

Written by Gary Johnson / Fact checked by Henry Speciale

how do you measure a bike frame

Do you find it hard to measure a bike frame because you do not know where to start? Having knowledge of how do you measure a bike frame is good practice. It comes in handy when you plan to upgrade your bike.

Knowing the proper process in measuring the bike frame will help you get a bike that goes perfectly with your body, promoting comfort throughout the ride.


What are the Guaranteed Ways in Measuring a Bike Frame Effectively


1. What You Need

You can use tape to measure. Remember that the bike frame size equates to the seat tube length in cm.

2. A Bike Frame’s Measurement

When you measure bike frame size, you should start from the middle of the tool crank to the upper part of the seat tube. Position the tape measure’s end on the actual midpoint of your bike’s crank.

You can then run the measuring tape to the tube’s end and measure up to that point. This will give the length of the seat tube or the frame size. To make the measurement more convenient, you can also remove the seat from the top pipe and put it away.

The usual size for a seat tube length ranges from 21 to 23 inches, or 53 to 58 centimeters.

After measuring bike frames size, you may want to decide whether it’s right for you. In this case, knowing your height and your inseam length/inside leg can help, as these measurements are often used in bike size charts.

Measuring your inside leg is not a challenge. In fact, doing it is easy if you know the process. You have to measure the length from the floor to your body’s crotch. While doing this, ensure that your legs are spread apart and that you are barefoot or wearing socks. Then, slowly spread your legs to about six to eight inches or 15 to 20 cm.

You can use a tape measure to find this distance. Ensure that you are measuring your actual crotch area and not just your pants. In short, you have to measure a bike frame to your height to get the right length.

Once you’re got your inseam length (in centimeters), you can get the ideal seat tube length by multiplying your inseam length. See instructions for different bike types below.

As for measuring your height, ensure that you removed your shoes and that you are standing up against a firm and straight wall. You can use a pencil to mark down your head’s level on the wall. Then, use a measuring tape to get the height of the marking.

3. Road Bike Frame Size

Road bikes are known for their centimeter measurements. That’s why U.S. citizens may have trouble with the sizes, since they got used to imperial ones. Dealing with this one is easy, though.

All you have to do is to multiply the length in inches by 2.54. You will get the proper measurement in centimeters.

Road Bikes are one of the most crucial bike types. Most of our time might be spent on a road bike’s saddle. That’s why our riding position usually plays a role in our comfort and performance.

After getting the length of your inseam, you need to convert it by multiplying the number by 0.7 to get your seat tube length. If you buy a bicycle with a seat tube equal to your inseam length, there’s a big chance for you to have difficulties pedaling.

Multiplying it by 0.7 will shorten the measurement, making it ideal for road bikes. With this, you can do uphill cycling and long trips with no struggles.

4. Mountain Bike Frame Size

Mountain bike frames, on the other hand, are left out with inches as measurement. They have tinier bike frames compared to road bikes. This gives the riders exquisite control as they can move and maneuver the bike even on challenging terrains.

For mountain bikes, you have to multiply the inseam length by 0.66. This bike type comes with thicker and bulkier tires. If we compare it to sleeker and more streamlined road bikes, a mtb gives a higher lift or elevation from the floor.

That’s why I highly suggest you multiply the inseam length by a smaller number to get the right mountain bike size and accurately measure bicycle frame size. You can use a calculator or a phone to do this.

5. Road Bike Vs. Mountain Bike

The difference lies in the seating position if we were to compare mountain bikes to road bikes. Sitting on a MTB allows you to sit more upright, where your arms are usually spaced wider apart. This makes your weight lean further towards the back.

This feature makes mountain bikes ideal for cycling on rough roads and other rocky terrains.

Finding the Right Size for Your Bike


When you measure bike sizes, it’s normal to feel awkward. Balancing is a real challenge as you may fall over by doing this. So, I highly suggest asking for help from your friends or partner.

After getting the bike frame size measurement, you can now buy your ideal road bike frame. Ensure that the values perfectly match your calculations. The numbers you got doing the math will correspond to the bike size perfect for your body fit.

You can also try out your chosen bicycle before buying. This will ensure that it gives off good comfort. Ride it around the park or any spacious lot, and you can adjust the seat until you notice that your leg is slightly bent when you push it down the pedal.

If you still feel awkward when reaching the pedals, you can always try other measurements until you determine the right ones for yourself.

Kid and Junior Bikes

A kid’s bike is in a different category as it uses wheels with measurements from 12 inches to 26 inches. You need to put a two-inch clearance on the uppermost tube for every junior bicycle.

On the other hand, smaller bikes with a wheel size of up to 20 inches would result in a naturally narrow stand-over height.

For more information on measuring a bike frame, you can check out this video.

Measuring Other Tubes

The Saddle Tube

I mentioned a seat tube earlier, and people are usually curious about this. So, what is really a seat tube? A seat tube is a long pipe where your bike saddle sticks. When you look at the area around this tube, you will notice a glued label showing the bike frame size.

It is usually seen three inches or 7.6 cm up from the chain sprocket. However, not all road bike frames label out their sizes. That is when the need for manual measurement comes in.

The measurement comes in two units, inches and centimeters. And the usual bike size usually ranges from 48 cm to 62 cm. The lower range of that sizing is for smaller riders, and tall bikers use 56 cm or more.

Measuring Top Tube Length

Bicycles used to have uniformly horizontal top tubes. But today, the evolution of design resulted in a sloping top tube for the majority of bikes.

You can look at a bike geometry table for some thorough guide that includes the actual top tube length of a bicycle. However, if you want a steady and reliable measure, you also have to estimate the horizontal cap tube length. This is called the virtual top tube length in most geometry charts and tables or the horizontal gap between your head tube’s centerline and the seat post.

Measuring this will mean using the clinometer app or your spirit level. This will ensure that the measured line is horizontal.

  • Stack and Reach

Most manufacturers usually label their reach and stack values for each bicycle. These values come with the advantage of being unrelated to the frame in terms of design. Plus, they can also measure the vertical distances between two main contact points: the head tube’s top area and the bottom bracket.

The reach is the horizontal distance between these two. It would require your spirit level to measure. You can position a plumb lining at the level’s end. Make sure that the string’s blob at the end is symmetrical and that the cord straightly hangs down. If you fail to do this, then your measurements may be off.

Then, you can line up the upper edge of your level with the middle line on the topmost part of your bike’s head tube. Carefully move the line to and fro until you notice that the plumbing line meets the middle of the lowest bracket spindle.

You can then measure the gap between the plumb line’s top area and the head tube. This will give you the reach measurement.

  • Measuring the Angles of Head and Seat Tube

Next, we will be talking about the seat tube and head tube angles. These two things are crucial determiners of proper and smooth handling. Usually, a more upright angle would lead to an agile control. A clinometer app would be very much practical in this area.

If you have a straight seating tube, it would be easy to measure your bike’s saddle tube angle. Do this by lining your phone and reading the number in the clinometer app. Ensure that the bicycle is in an upright position. It is also best if it stands on a horizontal surface for a more accurate analysis.

If you noticed a kink in your bike’s saddle tube, you need a straight rim that accurately follows the lining between the lowest bracket shell and the top part of the saddle tube. Use this part to line up your smartphone.


Now that I’ve discussed everything you need to know about How Do You Measure a Bike Frame, you can do your own thing. Riders can use a tape measure like the Amazon Basics Self-Locking Tape Measure to make their work easier.

  • Remember that there’s a big difference between a road bike and a mountain bike in terms of measurement.
  • Measure the height from the floor to your groin, ensuring that you are barefoot and your legs are slightly spread apart while doing the process.
  • A junior bike also comes with a unique type of measurement.
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