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Find out the answer to what size bike you need by using the easy calculator below (it may take a few seconds to load).
Simply select whether you want an adult or child bike, which type of bike, your height and your inseam length. You’ll then be presented with your recommended bike frame size.
It can often be a struggle decide just what size of bike to buy, especially if you’re shopping online and can only look at pictures of them on a screen. Unless you’ve seen them and tried them out previously, it can be a pretty big gamble.
Not least because it’s crucial to pick a bike with the right saddle height. If it’s too low, for instance, you can lose as much as 50 per cent force in your pedal power.
So, what’s the best way of determining what size to go for? With the help of this simple three-step guide, this should no longer be a problem for you at all.
Step One: What Type Of Bike Do You Want?
Of course, before anything else, the first thing to decide what you’re in the market for, because sizes will vary between different types of bicycles.
Not just men’s and women’s bikes, either; road and mountain bicycles differ greatly in sizing, and in some cases, so too do individual manufacturers. Here are some general rules to follow which you may find helpful:
- If it’s a road bike you’re after, the smaller size is normally your best bet, because it’s easier to make a small road bike bigger, either by raising the saddle or by fitting a longer stem, than it is to make a big road bike smaller.
- If you’re looking for a mountain bike, you’re probably a better off choosing the larger size, because you may otherwise find yourself feeling too cramped, for one thing. Also, a bigger mountain bike allows you greater freedom in shortening its stem if you wish to do so, wish can often improve handling.
- Usually, women’s bikes will have their own frame sizes. Since women generally have shorter upper bodies than men, their bikes will normally have shorter top tubes, meaning a female cyclist should feel less ‘stretched out’. This won’t affect the height of the saddle, though.
Step Two: Measure Your Height
There’s a simple, straightforward way to do this accurately.
Just stand upright on a flat surface against a wall, and take your shoes off. Then, leave a little pencil mark on the wall at the tip of your head, and then measure up from the bottom of the wall to see how tall you are.
If you want to double-check, there’s a second way of doing this, too, as follows:
Take your shoes off and stand with your legs roughly 15–20 cm (6–8”) apart. Measure your height from the ground to the top of your legs. Now, calculate the right size using the following formulae:
- Mountain bike – Leg inseam (cm) x 0.66 = your frame size
- Road bike – Leg inseam (cm) x 0.70 = your frame size
So, for example, if your leg inseam is 69cm and you want to buy a road bike, your frame size will be 48.3cm which, as you’ll see below, would mean you’d best suit an X-small road bike.
Step Three: Use a Height Guide
This won’t guarantee a perfect fit, partly because lots of manufacturers use their own sizing charts, but it’s one of the easier ways to decide which bike size is best suited to you.
Sizing will likely vary between different brands, but these can still be a good method of considering whether the frame will be too short or too big. Here’s a typical height guide you may find helpful:
| Height | Road Bike Size | Mountain Bike Size |
| 4’8” – 5’1” 143 – 155 cm | 17.3” / 44cm – XX-Small | 13.0” / 33cm – XX-Small |
| 5’1” – 5’4” 155 – 163 cm | 18.9”/ 48cm – X-Small | 15.0” / 38cm – X-Small |
| 5’4” – 5’7” 163 – 170 cm | 20.1” / 51cm – Small | 16.1” / 41cm – Small |
| 5’7” – 5’10” 170 – 178 cm | 21.3” / 54cm – Medium | 18.1” / 46cm – Medium |
| 5’10” – 6’0” 178 – 183 cm | 22.0” / 56cm – Large | 19.0” / 48cm – Large |
| 6’0” – 6’3” 183 – 191 cm | 22.8” / 58cm – X-Large | 20.1” / 51cm – X-Large |
| 6’3” – 6’5” 191 – 196 cm | 23.6” / 60cm – XX-Large | 21.0” / 53cm – XX-Large |
| 6’5” – 6’9” 196 – 205 cm | 24.4” – XXX-Large | 22.0” / 56cm – XXX-Large |
Once you’ve followed these three simple steps, you should be able to find the perfect size (or near-enough, anyway) for your new bike.
Any Other Pointers?
You might also want to try some of these ideas before deciding which bike to buy:
- It’s obvious and might make a lot of what you’ve already read above seem irrelevant, but sometimes, they can be no better test of whether you’re well-suited to a bike than by actually trying it out first yourself. Not only does it give you the chance to experience riding it, but you can also raise with staff members any particular questions or qualms you may have.
- Getting a professional bike fit is also a great idea, regardless whether you buy a bicycle in person from a shop or via the Internet. It will provide you with more detailed, accurate measurements, which can prove particularly helpful for athletes or beginner cyclists.
- Listen to your body. Pains in your lower back, elbow, neck or knee are all calling cards of a bad fit of a bike, as well as numbness. Don’t invest in something your body doesn’t feel comfortable with.
