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What Size Bike Do I Need? – Choosing the Perfect Bicycle

Choosing the bike that fits you can be difficult, especially if you want to shop online. A bike that’s too big can be hard to control, while one that’s too small can put too much pressure on your body.

If you’ve ever wondered how to choose the right size bike when shopping online, this article is for you!

What size bike do I need?

This is one of the most important questions. It helps you narrow down the choices and get on the right track. Do you plan to ride mostly on paved roads or mostly off-road? Will you be using it for commuting, leisure riding, or racing?

If you’re still unsure, check the different bike types and their physical characteristics below.

Road bikes

They are designed for speed and efficiency on paved roads. They typically come with a lightweight frame, thin tires, drop handlebars, and multiple gears. The upright riding position gives the rider more power while pedaling and provides better stability on long rides. Road bikes also are more aerodynamic than other types of bicycles, making them perfect for those who want to go fast. Road bikes usually also have a wider range of gears than other types of bicycles, allowing you to tackle hills and long distances with ease.

Gravel bikes

Gravel bikes share some similarities with road bikes, but they have specific features that make them suitable for both road and off-road cycling. These features may include additional clearance for wider tires and disc brakes. Gravel bikes are an excellent choice for riders who want to explore different terrains without committing to a specific type of bike.

Hybrid bikes

Hybrid bikes are designed to provide a versatile and comfortable riding experience that blends features of road bikes, mountain bikes, and touring bikes without being too specialized. They typically feature straight, flat handlebars and an upright riding position, similar to mountain bikes. However, they are lighter than mountain bikes and have narrow tires like road bikes, allowing riders to reach higher speeds with less effort. They often have racks and bags for carrying belongings. There are different hybrid bikes, including trekking, cross, commuter, city, and comfort, each suited for a particular use.

City bikes

City bikes, are recognized for their low-maintenance design. They are intended for moderately paced, short-to-medium-length rides in different weather conditions and are ideal for commuters cycling in urban areas. Their design emphasizes convenience and comfort over speed or the ability to navigate rough terrain. As a result, city bikes usually feature bigger saddles and elevated handlebars that support an upright riding position. They tend to be heavier than road bikes.

Mountain bikes

Mountain bikes, or MTBs, are specially made for off-road cycling. They commonly feature flat handlebars and wider tires that offer better shock absorption than narrower ones, making them ideal for balanced rides over uneven terrain. Compared to road bikes, MTBs usually have smaller frames, which make maneuvering easier and contribute to their suitability for off-road riding.

BMX bikes

BMX bikes are typically small and lightweight, making them ideal for performing tricks. They usually come with a single gear and 20-inch wheels that make extreme stunts easier. The frame is usually made of steel to withstand the rigors of intense jump landings or other stunts.

How can you figure out what size bike is right for you?

The easiest way to determine the size of a bike you need when buying online is to use the manufacturer’s size chart, which you can usually find in the product description. This chart typically requires two pieces of information: your height and/or your inseam length.

Step 1: Measure your inseam length

  1. Stand up straight with your back against a wall, wearing only your underwear or tight-fitting pants.
  2. Place a book between your legs, with the spine of the book facing up, as if you were sitting on a saddle.
  3. Hold the book firmly against the wall, making sure it’s level and not tilted.
  4. Using a pencil or marker, mark the spot where the book meets the wall.
  5. Measure the distance between the floor and the mark you made with a measuring tape or ruler.

This measurement is your inseam length.

Step 2: Measure your height

  1. Remove shoes or any bulky headwear that may affect the measurement.
  2. Stand up straight against a wall, with your back and heels touching the wall.
  3. Look straight ahead with your arms at your sides and your shoulders relaxed.
  4. Ask someone to place a flat object, such as a book or ruler on your head, making sure it’s level and parallel to the floor.
  5. While keeping the object level, measure the distance between the bottom of the object and the floor using a measuring tape or ruler.

This measurement is your height.

Step 3: Check out the manufacturer’s size chart

Every bike manufacturer offers its own size chart with their bikes. Usually, you’ll find the frame size in inches or centimeters along with a corresponding rider height range for each size.

Here’s an example of what a size chart might look like. Please note that this is just an example. Data may vary by manufacturer and bike type.

Mountain bike size chart

HeightBike SizeMarker
4’11” to 5’3” (150-160 cm)13 to 15 inches (33-38 cm)XS
5’3” to 5’7” (160-170 cm)15 to 16 inches (38-41 cm)S
5’7” to 5’11” (170-180 cm)16 to 17 inches (41-43 cm)M
6’0” to 6’2” (180-188 cm)17 to 19 inches (43-48 cm)L
6’2” to 6’4” (188-193 cm)19 to 21 inches (48-53 cm)XL
6’4” or taller (193+ cm)21 plus inches (53+ cm)XXL

Step 4: Calculate your basic frame size

You can also calculate your bike size considering your inseam length.

Multiply your inseam length (in centimeters) by a factor to estimate your initial frame size. The factor you use depends on the type of bike you’re looking for:

  • Road Bikes/Gravel Bikes: Multiply inseam length by 0.65.
  • Mountain Bikes: Multiply inseam length by 0.66.
  • Hybrid/City Bikes: Multiply inseam length by 0.67.

The result gives you an initial frame size in centimeters.

How to measure for a kid’s bike?[1]

Similar to measuring for adult bikes, start by measuring your child’s inseam. Have your child stand with their back against a wall and their feet slightly apart. Measure the distance from the crotch to the floor. This measurement will help you determine the appropriate bike size.

Use the Wheel Size as a Guide

Wheel size rather than frame size typically categorizes kids’ bikes. The wheel size is a good indicator of the bike’s overall size and intended rider age range. Common kids’ bike wheel sizes include 12″, 16″, 20″, and 24″.

Select the Right Wheel Size

Choose a bike with a wheel size that corresponds to your child’s inseam measurement and age. Here’s a general guideline:

  • 12″ Wheels: Suitable for kids with an inseam of around 14-17 inches. Typically, these bikes are for ages 2 to 4.
  • 16″ Wheels: Suitable for kids with an inseam of around 18-22 inches. Generally for ages 4 to 6.
  • 20″ Wheels: Suitable for kids with an inseam of around 22-25 inches. Typically for ages 6 to 10.
  • 24″ Wheels: Suitable for kids with an inseam of around 24-28 inches. Generally for ages 8 to 12.


Q: What if I’m between sizes?

A: Think about the type of riding you’ll be doing. If you prefer a more aggressive and performance-oriented riding style, you might lean towards the smaller size for a more maneuverable bike. On the other hand, if you prioritize comfort and stability, the larger size might be a better choice.

Q: Does measuring for a BMX bike different?

A: Yes, BMX bikes are measured differently due to their smaller frame sizes and wheel diameter. When trying to determine the right size for a BMX bike, look for the standover height of the top tube. The rider should be able to stand over this comfortably with both feet flat on the ground. It’s also important to make sure that your handlebars are at a comfortable height. You can raise or lower the seatpost to achieve this. Adjusting the handlebars to fit your personal style is also important for comfort and maneuverability. Finally, remember that BMX bikes run on shorter chain stays than other types of bikes, so you may need to adjust the crankset length accordingly.

What to do next?

If you plan to purchase a new bike, consider browsing our top picks of bikes to find the one that suits your riding style. You can also check out our guide on how to store your bike outside to get more helpful tips.

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Mate is a passionate bikepacking enthusiast and the founder of this website. He loves exploring new destinations, admiring nature, and engaging in outdoor activities. He strongly believes that healthy living should be environmentally friendly too, which is why he prefers to use bicycles for his transport needs.