How to Determine Your Bike Size

By : Mr Mamil
Updated :

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Getting the bike size right is absolutely essential for your riding comfort, enjoyment, safety, and injury prevention. There is no one-size-fits-all when it comes to road bikes.

Road bikes need to cater to cyclists from 5’ (150cm) to 7’ (210cm). Bike manufacturers such as Specialized and Trek offer up to seven sizes to cater to such a wide height range.

Finding out the correct bike size can sound like a daunting task, especially for beginners. But it really is not once you’ve spent some time getting to know the various terms used in the geometry charts.

In this article, we’ll discuss six methods you can use to determine the right bike size for yourself.

Method 1 – Inseam and standover height

This is the most basic and widely used method and is especially suited for beginners.

Measure your inseam length and compare it against the geometry chart of the bike frame you’re after. Here’s a quick way to do it.

  1. Stand barefooted against a wall with your feet 6” apart.
  2. Place a book between your thigh and raise it up until it’s snug against your crotch.
  3. Make a mark where the top of the book touches the wall.
  4. Measure the distance between the floor and the mark.
  5. Convert the measurement to millimeters. This is your inseam measurement.
  6. Go to the bike manufacturer’s website and search for the bike frame you want.
  7. Search for the geometry chart. Note that each frame model might have a different geometry chart.
  8. Compare your inseam measurements against the standover height.
  9. Choose a bike frame size that has a standover height between 25 to 50mm lesser than your inseam measurement.
  10. If you’re right in between sizes, you want to err on the side of caution and opt for smaller frame size.

Method 2 – Visit a reputable bike shop

All reputable bike shops worth their salt should be able to tell the right frame size for you quickly. Visit a shop that carries the specific brand you want because they have the product and brand experience.

Chat with the salesperson to have a feel of their experience and expertise. Be careful that some shops might try to hard-sell you a bike size that’s not ideal for you. Do some research beforehand and ask a lot of questions if unsure.

More reading : Buying Bikes Online vs Locally

Method 3 – Get a professional bike fit

Many cyclists only have their bike fit after purchasing their bike. There would be nothing wrong with that unless they purchased the wrong bike size. If the bike size is correct, all the adjustments and tweaks will be around the reach, saddle height, and cleat positioning.

If you can get a bike fit before purchasing, that would be ideal.

The bike fitter will use an adjustable fitting bike such as Retul instead of your actual bike (which is yet to be purchased). The bike fitting process also takes into consideration your previous injury history, physical imbalance, and riding preference.

Let them know the bike models you’re planning to purchase and they can advise your ideal frame size, handlebar width, and stem length combination.

Most high-end road bikes today come with a one-piece handlebar stem, and it’s important that you get this right. Otherwise, it’ll be expensive to get new ones as they typically start from $500.

Method 4 – Online calculators

There are online bike fit calculators such as the one from Competitive Cyclist, Jenson USA, or Pedal Force.

The tool will guide you to take measurements such as inseam, sternal notch, height, upper/lower arm, upper/lower leg, and torso length. You can easily do this at home and input the values into the tool.

The tool will output a number of length measurements, and you’ll need to compare them against the geometry chart of the bike you’re after.

A word of caution. Online calculators should only be used as a general guide, and you should never rely on its result for your final decision.

Method 5 – Compare with friends

Ask and observe the cyclists in your local bunch. Look for telltale signs such as,

  • Is there anyone riding the same brand/model of bike that you’re after?
  • Do they have a similar height (eg: 1.5cm shorter/taller)?
  • How is their bike set up?

Generally, if two cyclists are of similar height (up to 1.5cm difference), they will ride the same size of bike. The only difference lies in the saddle height, saddle setback, and stem reach.

Method 6 – Use your existing bike as the benchmark

This method assumes that you currently own a bike that’s properly fitted to you. Compare the Stack and Reach measurements between the old and new (to be purchased) bike. If your current bike size is not ideal, then don’t skip this method.

Each bike brand (and model) has slightly different measurements. You want to pick a frame size with Stack and Reach measurements that are the closest to your existing bike.

Method 7 – Use Mr. Mamil’s guide

I’ve combed through the various bike manufacturers‘ bike sizing guides to develop this size chart guide.