Establishing the correct bike size for you is one of the most important things to do when buying a new bicycle. Although theres a lot you can adjust on a bike so that it fits better, if you start off with a frame thats too small or too large for you, you may be placed awkwardly and uncomfortable as you ride.That can result in aches and pains when cycling and your bike not handling as it should, both of which can limit your enjoyment when out riding.With that in mind, heres everything you need to know about bike sizes be it a mountain bike, road bike, hybrid bike, women's-specific bike or childs bike. Bike size chartWell cover the nuances of road bike, mountain bike, hybrid bike and gravel bike sizes shortly, but heres an overview of typical frame sizes, according to rider height.However, body dimensions and frame layouts can vary significantly from one person and brand to the next, so seek further advice, specific to the bike you are intending to buy, before purchasing. Rider height (cm)Rider height (feet)Road bike frame size (cm)MTB frame size (inches) 143155cm4ft 8in 5ft 1in44cm13in 155163cm5ft 1in 5ft 4in48cm15in 163170cm5ft 4in 5ft 7in51cm16in 170178cm5ft 7in 5ft 10in54cm18in 178183cm5ft 10in 6ft56cm19in 183191cm6ft 6ft 3in58cm20in 191196cm6ft 3in 6ft 5in60cm21in 196205cm6ft 5in 6ft 49in62cm22in Edit Table How do I know what size bike I need?More accurate ways of measuring your height are available. - Getty ImagesThere are a number of ways to find your correct bike size.1) Rider height and inside legThe quickest method is often to look on a brands site.Usually, there will be a chart with recommended bike sizes for different rider heights, so its comparatively easy to see where you fit.Some brands will have an interactive size guide, where you input your height and often other details, such as inside leg length, to find your recommended size.However, don't take a brand's size guide as gospel it's a guide, after all, and one person's dimensions and requirements can vary from another, even if they are the same height.Equally, if you are between sizes, you will need to decide whether to size up or size down. More on that to come. 2) Go to your local bike shopNext up, if youre buying a bike from a physical shop, you can ask them what size you need. Sometimes, youll just get eyeballed and the assistant will put you on a bike to see if you fit.However, bike shops are getting more sophisticated, so you might get a proper sizing, where the shop staff will measure you and determine more precisely what size bike you need.Find a good local bike shop that takes the time to ensure youre buying the right size bike.3) Bike fitFinally, some shops will offer you a discounted or free bike fit as part of your purchase. This is the most sophisticated option, not only to make sure you get a frame that fits, but to have your contact points set correctly so you'll be comfortable and efficient when riding.You may be advised to swap out components such as the stock saddle for something that better suits your sit bone anatomy or to opt for a non-standard bar width or stem length, for example.A bike fit will also help you to determine key setup measurements, such as saddle height, which are crucial to finding a comfortable and efficient riding position. Well cover this in more detail later.What if I'm between sizes?Theres normally an overlap between frame sizes, so youll often have a choice of two sizes.If you sit between two frame sizes, the common advice is to take the smaller of the two options. Theres a lot you can adjust easily on bikes, such as saddle height, saddle setback and handlebar height, to fine-tune the fit.However, seek further advice from the bike brand or your local shop, if you're unsure.Road bike size guideNaming conventions for bike sizes vary by brand. - Our MediaThe most common way of sizing road bikes is by seat tube length in centimetres.However, this will be different depending on whether the frame has a sloping or a horizontal top tube, so youll often see 'effective' seat tube lengths quoted, based on a horizontal line between the head tube and the seatpost.Some brands just give you S, M, L (and often XS and XL) sizes. Others, such as Colnago and Pinarello, have their own unique sizing systems.That means youll need to revert to the brands size info, as described above, or study the road bikes geometry chart to work out which bike size is best for you.See our guide to road bike sizing for more detailed information. Rider heightFrame size Feet and inchesCentimetresEffective top tube (cm)Bike size 4ft 10in 5ft148-15247-48XXS 5ft 5ft 3in152-16049-50XS 5ft 3in 5ft 6in160-16851- 3S 5ft 6in 5ft 9in168-17554-55M 5ft 9in 6ft175-18356-58L 6ft 6ft 3in183-19158-60XL 6ft 3in 6ft 6in191-19861-63XXL Edit Table Mountain bike size guideMountain bike brands largely stick to 'T-shirt sizing'. - Our MediaWhen it comes to mountain bike sizing, most brands have reverted to an S, M, L (etc) sizing method for their frames.With mountain bike seat tube lengths being highly dependent on the frame geometry and rear-suspension layout, T-shirt-style sizing provides the clearest guide.The trend for long and slack mountain bike geometry has accentuated the difficulty in selecting a frame size based on seat tube length alone and some brands now rely on reach (the horizontal distance from the centre of the bottom bracket to the top of the head tube) to define their frame sizes.Seat tube length is still an important consideration though, because you need to be able to get your saddle height right. If you want to fit a dropper post, a short seat tube may also mean some models won't fit.Finally, MTB frame sizes are significantly smaller than for road bikes, so dont try to compare your road bike and mountain bike sizing.Weve got a lot more info in our mountain bike sizing guide. Bike sizeFrame sizeRider height Extra-small13-14in152-162cm (5ft 5ft 4in) Small14-16in162-170cm (5ft 4in 5ft 7in) Medium16-18in170-178cm (5ft 7in 5ft 10in) Large18-20in178-185cm (5ft 10in 6ft 1in) Extra-large20-22in185cm plus (6ft 1in plus) Edit Table Mountain bike sizing, geometry and riding styleIts a good idea to study our guide to mountain bike geometry to understand the key measurements of an MTB frame, and how they affect a bikes handling characteristics and fit.The type of riding your bike is designed for alters its geometry, too. If youre riding a cross-country bike, designed for agile handling, you may want to be more stretched out, while beginners may prefer a shorter reach so that theyre more upright, with less strain placed on the hands and wrists.Bikes designed for more aggressive riding, including the latest downcountry bikes, trail bikes and enduro bikes, will typically have a longer, slacker geometry to match, which may have a knock-on impact on finding the correct frame size.With the trend for bikes to have slacker head tube angles, its important to get your position forward enough to weight the front wheel and the suspension effectively, so you dont want a frame and seat position that sits you too far back. Again, a geometry chart is the best way to work out the best frame size for a comfortable fit.Gravel bike size guideGeometry becomes particularly important when choosing a gravel bike. - Our MediaGravel bike sizing is much like road bike sizing, with most brands using the seat tube length in centimetres to size frames, though T-shirt-style sizing is, once again, also used by some brands.In general, your position on a gravel bike will be more relaxed and upright than on a road race bike.Thats because you need to be able to shift your weight around more off-road to balance and steer your bike over obstacles. A more upright position will also be more comfortable over uneven terrain.Having said that, if youre interested in gravel racing, a longer and lower position will reduce your frontal profile and potentially make you faster, and the geometry of many of the latest go-fast gravel bikes is shaped accordingly.As when choosing a road bike, pay attention to the geometry of a gravel bike when choosing your next ride. Buying a bike that matches your riding intentions is vital. Rider heightFrame size Feet and inchesCentimetresEffective top tube (cm)Bike size 4ft 10in 5ft148-15247-48XXS 5ft 5ft 3in152-16049-50XS 5ft 3in 5ft 6in160-16851- 3S 5ft 6in 5ft 9in168-17554-55M 5ft 9in 6ft175-18356-58L 6ft 6ft 3in183-19158-60XL 6ft 3in 6ft 6in191-19861-63XXL Edit Table Womens bike size guideBrands that create women's-specific bikes tend to have specific size guides. - Sam Voaden / Our MediaWomen's frame sizes can vary significantly depending on a brand's outlook on women's bikes.Some brands, such as Liv, have womens-specific geometry and womens bike ranges designed from the ground up. As a result, the range of sizes on offer will also be specific to women.Other brands, meanwhile, assert that there are more differences in body proportions among people of the same sex than there are between sexes, and label all their bikes as unisex as a result, following a 'unisex' size guide.In the middle, you have brands that offer 'unisex' frames but with specification tweaks to cater for women.Some brands such as Canyon, on its women's-specced WMN road bikes fit smaller 650b wheels to their smaller frame sizes, so that geometry and handling can be kept consistent through the range.Weve got a separate guide to womens bike sizing to cover the topic in detail, including the difference between road, mountain and hybrid bike sizes for women.Kids bike size guideAs with adult bikes, its vital to get the size correct for a child's bike.Age range is often quoted by bike brands as a way to size kids bikes but, because children grow at different rates, its not the best way to make sure a bike will fit comfortably.Measuring your childChildren grow quickly, but ensuring they are riding the correct-size bike will make for a more positive experience. - andresr / Getty ImagesMeasuring your child is an important first step in choosing the right kids bike size.That starts off with their inside leg measurement. You also need to measure their height.For the majority of the best kids bikes, that should give you the info you need to hone in on the correct bike size.Wheel sizesWhen buying a kids' bike, you'll find they're sold by wheel size. - Our MediaAs we cover in our kids bike size guide, childrens bikes are normally sold by wheel size (in inches), with sizes increasing from 12-inch balance bikes, via 14in, 16in, 20in, 24in and 26in. Approx age Wheel size (in)Minimum inseam (in)Minimum inseam (cm)Minimum height (ft, in)Minimum height (cm) 2+12 (balance bike)12302,888 3+1415383,398 4+1616423,5104 5+1818463,8112 6+2020523,11120 8+2423574,2127 10+2625644,7140 Edit Table What if a child is in between sizes?Its tempting to buy a size up so that theyll grow into it in a few months. Thats not optimal, not least if you're teaching a child to ride a bike for the first time.If theyre not able to ride the bike comfortably and put a foot down easily, they may feel nervous, lose confidence, and be put off riding. Its also easier for a child to overbalance and have a fall if the bike is too large for them.Some brands have trade-up schemes with a discount on a larger bike when theyve grown out of their current one.How are bike sizes measured?Sizing conventions can vary between one type of bike and another, and between one brand and another. - Our MediaBike sizes are measured in a number of different ways and, confusingly, theres little consistency between bike types or between brands.Road bike sizes are typically measured in centimetres, based on the length of the seat tube (from the bottom bracket to the top tube), although as well see the actual seat tube length will vary dependent on the frame geometry.A bike frame's size is often determined by the length of the seat tube, which runs from the bottom bracket to the top tube. - Simon Bromley / Immediate MediaOn the other hand, mountain bike frame sizes are typically measured in inches, because they originated in the US.You cant compare mountain bike frame sizes directly to road bike frame sizes not just because theyre in different units of measurement, but also because the frames on mountain bikes usually have much shorter seat tubes than those found on road bikes.To get around the difficulty of measuring frame sizes, some brands use T-shirt sizing (e.g. S, M, L) for all their bikes, based principally on rider height.But again, this measure isnt consistent between brands. Indeed, brands that sell both road and mountain bikes may use a different sizing convention between the two.Childrens bikes use different sizes again, often based either on a childs age or the bikes wheel size.How to find your bike's sizeIf you have a current bike, you can look at the frame size sticker on it to find what size it is. This will often be located on the seat tube, but might be in a more discreet location, such as under the bottom-bracket area.If its a recently sold model, you should be able to find a geometry chart for your frame on your bike brands website.Alternatively, you can measure your frame size yourself, as we explain in this piece on how to measure a bike frame.