how to measure bike size

How to Measure Bike Size Correctly for the Perfect Ride

Last Updated on

Bicycles are a great way to stay active and explore the world. When you’re ready to buy one, there’s a lot to consider: style, color, and price. But what about bike size?

The right size will make all the difference in your ride! Here, we’ll teach you how to measure bike size correctly. This guide will also break down everything you need to know about getting the right bike frame size and essential terms like inseam, top tube length, and seat tube length.

After reading this article, our goal is that you’ll know how to tell the size of a bike and how to measure a bike size for adults and kids!

Determining Bike Size Based on Height and Inseam

If you’re looking for the right size bike that allows for excellent control, you’ll want one that is roughly your inseam length plus about an inch or two.

When picking out bike size, it’s essential to know the following:

  • the type of bike that you ride or are interested in
  • your measurements, such as your height and inseam.

Your Riding Style and the Bike That You Ride

Knowing the type of bike that you ride is important because the sizes of bike frames are not universal.

For example, if you ride a mountain bike, you will probably need smaller or medium-sized bike frames. Conversely, if you want to buy a road bike, the frame you should look for will be larger.

Your Measurements

Your bicycle size is based on your height, inseam measurement, and reach. You cannot tell the size of a bicycle without taking these body measurements.

You can measure your height easily by standing up straight against a wall, then having someone measure the distance between your head and the floor.

You will need someone to assist you when measuring your inseam. To measure your inseam length:

  • Standing with your back against the wall
  • Have a friend measure from your groin to the floor

You can also measure the inseam length by standing with legs hip-width apart. Then, with a bent leg on a chair, have your companion measure the distance between the floor and the top of your knee.

Now that you know your height and inseam measurements, you can refer to an appropriate bike size chart to determine the frame size that’s ideal for you. Keep in mind that there’s a bike size chart per bicycle type. This means there’s a specific bike size chart for city bikes, road bikes, and mountain bikes.

Another measurement that is equally important is your reach because your arm’s length and bike’s reach must align correctly. Reach, determined by your ape index, will affect how you control your ride.

You can find out whether you have a short or long reach by comparing your arm length against your height. A greater arm span means a positive ape index and a longer reach.

Measuring Bike Frame Size

But what if you already have a bicycle that fits you perfectly and you just need a new bicycle frame in the same size? This section will teach you how to determine size of bike frames.

To measure a bicycle’s frame, you’ll need the following materials:

  • Tape measure
  • String or duct tape

Step 1: Measure the Top Tube Length

To measure the top tube length, start by wrapping the bicycle’s frame with tape to protect it. Then, measure between the center of each end of the top tube where your seat post and handlebars are located.

Step 2: Measure the Seat Tube Length

To do this, you’ll have to remove the seat and handlebars. Measure from one end of the bike seat tube where the stem is located to another point a few inches up, just before you’d expect it to be.

Step 3: Measure Your Bike’s Reach and Stack

Stack refers to how high your handlebars are in relation to the frame size. To measure it, extend a piece of string over one end of the bike top tube, then pull up until that point reaches another part on your frame.

The reach is the horizontal distance between the top tube and the seat tube. The reach is measured by extending a string from the bike’s top tube to the seat.

Step 4: Measure the Wheelbase

Measuring the bike’s wheelbase is a bit different from other frame size measurements.

To get the wheelbase, measure the distance between the bicycle’s front and wheel axles. Bear in mind that you need to keep the fork straight ahead for accuracy. If the fork is not straight, you can use a string to measure the bicycle’s wheelbase on both sides and obtain the average.

Step 5: Measure Your Bicycle’s Chainstay Length

The best way to determine your bike’s exact chainstay length is by using a ruler that has been precisely calibrated for this purpose which you can find at most shops.

The chainstay length is crucial because it will determine how the bike handles. The shorter the chainstay, the easier your bicycle will be to maneuver, but this may come at a price of stability.

The longer chainstay, the more stable bikes will feel when riding over rough terrain and uphill.

Step 6: Measure the Front Center

Measuring a bike’s front center is important because, as with any frame size, the shorter the front center of a bicycle, the more maneuverable it becomes. A longer front center will add stability when riding uphill or over challenging terrain.

The front center is measured by getting the distance between the axle and the bike’s front dropout.

Step 7: Measure the Bike Frame’s Angles

Measuring a bike’s head tube and seat tube angles is important because it helps you determine whether it is suitable for your body type.

Using your clinometer app, measure the bike’s head tube angle by placing your phone at the bike’s top tube. Your bicycle should be vertical when you do this.

Seat tube angles are measured by how much they are angled forward or backward from vertical. The industry uses two standards for measuring this, either in degrees (usually between 72-74°) or millimeters of offset.

To measure the seat tube angle, position the bike as if you were riding it. Then, using a clinometer app, you measure the angle by placing your phone at the top of the seat tube.

Step 8: Measure the Bottom Bracket Drop and Height

This is the difference between the height of the wheel axles and the centreline of the crank axle. It is measured by using a bike ruler.

To measure the drop, measure the heights of both the bottom bracket and rear axle and then get the difference between the two measurements.

The bottom bracket’s height, on the other hand, is the vertical distance between the ground to the centermost part of the bracket’s shell.

How to Measure a Kid’s Bike Size

When looking to purchase kids’ bikes, you need to measure your child’s bike size. Most bike shops provide a bike sizing tool for you to get your child’s inside leg measurement.

Once you have measured his or her bicycle size, check with local retailers for kids’ bikes that fit this frame size. If they are within three inches of the bike size, they should fit comfortably on the bicycle.

If your child is between sizes, you can purchase an additional seat post extender to make up for the difference in bike size. If there are more than three inches of frame length differences, consider purchasing a kids’ bike with adjustable frame sizing components like quick-release levers that allow for adjustments.

Bikes that are two bike sizes above a child’s ideal size will often be too big for a safe bike ride. Larger bikes may also inhibit their ability to maintain balance and control while riding.

As your child grows, you can simply adjust the seat height of his first bike up by using the quick-release levers or sizing tools.

Important Things to Remember When Measuring Bike Size

Getting a bike in the correct size is paramount to riding safety and enjoyment. Here are several things you need to consider when measuring bikes.

Bike Frame Measurements Affect Performance and Comfort 

The size you choose will impact how it handles, performs on hills, and speeds up or slows down while riding it. Thus, it is important to choose the frame size that will work best for your height, build, and body type.

When Buying a New Bike, Measure Your Current Bike First

When looking to buy a new bike, always measure your current bike first. This way, if there is an issue with the bicycle’s frame size not fitting correctly, you will have something to use while waiting for the perfect bike.

Bike Frame Size Is Not the Same as Clothing Size

Many people assume that frame sizes for bikes and clothing sizes correspond. However, this is a misconception that can lead to buying incorrect frames or having unnecessary issues with bike fit.

Different Bike Types Vary in Terms of Frame Sizes

When it comes to sizing, different bikes require different measurements for bicycle frames. Thus, bike frame size measurements can vary depending on the model you choose to ride and how it fits your height and weight.

For example, if you are looking for mountain bike frames, the size measurements are different from those of road bikes.

A Proper Bike Fit Makes Riding Safer

A correct bike fit will make your riding experience safer, more comfortable, and efficient with less fatigue. Hence, make sure to measure your bicycle’s frame size correctly, particularly when buying one online.

Bike sizing is more about your comfort. Hence, it’s also important that you choose a bike size that allows both of your feet to touch the ground. You should be able to sit comfortably without having to scoot forward or backward.

Bike Fitting Should Not Be Skipped

Getting a professional bike fit is an important step towards buying the right size bike. It should not be skipped so you can shop for the right frame size, which will result in a more comfortable and safe ride.

You cannot determine whether or not a bike fits correctly without getting on it at the bike shop and on the test ride.

That said, bike fitting is not just about measurements. It also involves how comfortable you will feel when you ride bikes for long periods. You don’t want to waste money on the wrong size bike.

Road Bike Frames Are Different From Mountain Bike Frames

Road bike frame sizes are very different from mountain bike frame sizes. You want a more upright and comfortable model to ride for extended periods on the saddle for road bikes.

To determine your ideal bike size measurement for this type of bike, measure your inside leg length and standover height while straddling the bike.

The sizes for mountain bike frames, on the other hand, vary depending on bike type and rider preference for a bike fit.

To choose your best bike size measurements, you should measure inside leg length while standing over the bike with boots touching the pedals in a low gear position (like how it would be when riding).

The bike height, bike stack, and reach measurements should be taken into account as well.

Frequently Asked Questions on Bike Sizes

How Accurate Are a Road Bike Sizing Chart and a Bike Fit Calculator?

Road bike sizing charts are only meant as a rough guide for getting the right frame size.

A bike size chart, regardless of bike brands and types, only provides an estimate of your ideal bike size based on your height and inside leg measurement. Most manufacturers have their own size chart as well.

A bike fit calculator will help determine the right bike size for you based on your height and inseam measurements.

What Is the Best Bike Sizing Method?

The most accurate bike sizing method is done by a professional bike fitter or at your local bike shop using a few different bikes, saddles, stems, handlebars, and other components. This helps ensure you have the right tool for getting bike sizing measurements correctly. It is undeniable far more accurate relying on bike size charts and calculators.

What Is the Average Frame Size and What Size Should I Buy?

Bike frame sizing varies depending on bike type and whether it’s for hybrid bicycles, mountain bikes, or road bikes.

The bike size you choose depends on your personal preference and what works best for your height, build, and body type.

Consider your riding style, comfort preference (upright or aggressive), and usage if you’re a beginner.

I Am Interested in Mountain Biking. What Frame Size Should I Buy?

It’s recommended to get a bike fit by experts. Your local bike shop can recommend an expert who will help choose a mountain bike’s frame size for you.

Otherwise, you can use an online sizing tool or free bike size calculator available to give you an estimate of what is the right bike size measurement for you.

Remember that mountain bikes are designed for off-road riding and biking on uneven terrain, so you should consider the frame design, wheel diameter, wheel size, and overall maneuverability as well.

The Right Bike Size for a Perfect Fit

When it comes to buying bikes, size matters. Thus, get your measurements so that the bike fits snugly against your body as you ride. Your measurements will also help ensure that there’s a perfect fit for everyone, no matter how tall or short you are!

Have any questions on how to measure bike size correctly? Let us know in the comments. We are here to provide expert advice for those who need guidance in regards to sizing up bikes.

Additional Resources

About The Author

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top