What size bike do I need?
Drag the sliders. Your recommended frame size updates live, for road, mountain and hybrid geometries, with the same formulas bike fitters use.
Medium, add inseam for a more precise fit
- Estimated inseam (82cm) from height, measure your inseam below for better accuracy
- For road bikes, a XL frame (61-63cm) should fit your measurements
- This is a starting point, brand geometry varies, so always cross-check the manufacturer size chart
- Always test ride and consider reach/stack for perfect fit
Frame size isn't one number.
Frame size, sometimes called frame height, describes the geometry of the bike. It dictates how you sit, how far you reach, and how the bike handles. Get it right and the bike disappears underneath you. Get it wrong and every ride is a negotiation with your own knees, wrists and back.
Manufacturers express it in centimetres, inches, or letter sizes from XXS to XXL. Each captures different aspects of the frame, so understanding your measurements, and knowing that brands don't agree on what “Medium” means, is how you end up on the right bike.
Three formulas. Decades of bike fits.
Road bikes
The LeMond formula, developed by three-time Tour de France winner Greg LeMond. Still the starting point for most traditional road fits, particularly frames with a level top tube.
Mountain bikes
Standard MTB formula. Mountain bikes use inches and have sloping top tubes with more stand-over clearance for technical terrain and quick dismounts.
Hybrid & gravel
Adjusted for more upright geometry and relaxed positioning. Used for commuter, touring and gravel bikes where comfort tends to trump outright aerodynamics.
General size chart.
Your height row highlights automatically as you move the slider above. ✓ = good fit, △ = acceptable,, = not recommended.
| Height | XS | S | M | L | XL | Inseam |
|---|---|---|---|---|---|---|
| 147–160 cm (4'10"–5'3") | ✓ | , | , | , | , | 66-76cm |
| 160–170 cm (5'3"–5'7") | △ | ✓ | , | , | , | 76-81cm |
| 170–180 cm (5'7"–5'11")You | , | △ | ✓ | , | , | 81-86cm |
| 180–188 cm (5'11"–6'2") | , | , | △ | ✓ | , | 86-91cm |
| 188–200 cm (6'2"–6'7") | , | , | , | △ | ✓ | 91-96cm |
Measure your inseam.
Accurate inseam is the single biggest improvement you can make to a sizing result. Do it barefoot, against a wall, and measure twice, it's five minutes well spent.
Stand barefoot against a wall with your feet 6–8 inches (15–20 cm) apart.
Place a hardcover book between your legs, spine pressed firmly up against your crotch (simulating a saddle).
Mark the wall at the top of the book with a pencil.
Measure from the floor to the mark in centimetres, that is your inseam length.
- Tip. Have someone help you for best accuracy. Measure 2–3 times and use the average.
Brand geometry varies.
These formulas are a reliable starting point, but every manufacturer uses different geometry. A size M from one brand can fit very differently from a size M from another. Before you commit, always cross-check against the manufacturer's own size chart and, if possible, test ride the bike. Modern geometry also focuses on reach and stack, these numbers matter more than traditional seat-tube length once you're between sizes.
Three fit checks after you size up.
Stand-over height
2–3 cm clearance between the top tube and your body when standing flat-footed.
Saddle position
Slight bend in the knee at the bottom of the pedal stroke, never fully straight, never cramped.
Handlebar reach
Comfortable arm extension without overreaching or feeling compressed on the drops.
Frame size charts.
Don't have your inseam to hand? Use these height-based charts as a quick guide. The row matching your current slider height is highlighted in each table.
Mountain bike sizes
| Height | Recommended frame size |
|---|---|
| 150–155 cm (4'11"–5'1") | 33 - 36 cm / 13" - 14" |
| 155–160 cm (5'1"–5'3") | 35 - 38 cm / 14" - 15" |
| 160–165 cm (5'3"–5'5") | 38 - 40 cm / 15" - 16" |
| 165–170 cm (5'5"–5'7") | 40 - 43 cm / 16" - 17" |
| 170–175 cm (5'7"–5'9") | 42 - 45 cm / 16.5" - 17.5" |
| 175–180 cm (5'9"–5'11")You | 44 - 47 cm / 17.5" - 18.5" |
| 180–185 cm (5'11"–6'1") | 46 - 49 cm / 18" - 19" |
| 185–190 cm (6'1"–6'3") | 49 - 52 cm / 19" - 20.5" |
| 190–195 cm (6'3"–6'5") | 51 - 56 cm / 20.5" - 22" |
| 195–200 cm (6'5"–6'7") | 54 - 58 cm / 21.5" - 23" |
Road bike sizes
| Height | Performance / racing | Triathlon |
|---|---|---|
| 155–160 cm (5'1"–5'3") | 47 - 49 cm | 46 - 48 cm |
| 160–165 cm (5'3"–5'5") | 49 - 51 cm | 47 - 49 cm |
| 165–170 cm (5'5"–5'7") | 51 - 53 cm | 48 - 50 cm |
| 170–175 cm (5'7"–5'9") | 53 - 55 cm | 50 - 52 cm |
| 175–180 cm (5'9"–5'11")You | 55 - 57 cm | 52 - 55 cm |
| 180–185 cm (5'11"–6'1") | 57 - 60 cm | 55 - 57 cm |
| 185–190 cm (6'1"–6'3") | 60 - 62 cm | 57 - 60 cm |
| 190–195 cm (6'3"–6'5") | 62 - 64 cm | 60 - 62 cm |
| 195–200 cm (6'5"–6'7") | 64 - 66 cm | 62 - 64 cm |
Hybrid bike sizes
| Height | Recommended frame size |
|---|---|
| 150–160 cm (4'11"–5'3") | 42 - 48 cm (XS) |
| 160–170 cm (5'3"–5'7") | 48 - 52 cm (S) |
| 170–175 cm (5'7"–5'9") | 52 - 55 cm (M) |
| 175–180 cm (5'9"–5'11")You | 55 - 58 cm (M/L) |
| 180–185 cm (5'11"–6'1") | 58 - 61 cm (L) |
| 185–190 cm (6'1"–6'3") | 61 - 63 cm (XL) |
| 190–195 cm (6'3"–6'5") | 63 - 66 cm (XL) |
| 195–200 cm (6'5"–6'7") | 65 - 68 cm (XXL) |
Gravel bike sizes
| Height | Recommended frame size |
|---|---|
| 150–160 cm (4'11"–5'3") | 42 - 47 cm (XS) |
| 160–170 cm (5'3"–5'7") | 47 - 50 cm (S) |
| 170–175 cm (5'7"–5'9") | 50 - 53 cm (S/M) |
| 175–180 cm (5'9"–5'11")You | 53 - 55 cm (M) |
| 180–185 cm (5'11"–6'1") | 55 - 58 cm (M/L) |
| 185–190 cm (6'1"–6'3") | 58 - 60 cm (L) |
| 190–195 cm (6'3"–6'5") | 60 - 63 cm (XL) |
| 195–200 cm (6'5"–6'7") | 62 - 65 cm (XXL) |
Children's bike sizes
| Age | Height | Wheel size |
|---|---|---|
| 2 - 3 years | 85–100 cm (2'10"–3'3") | 10" - 12" |
| 3 - 5 years | 95–110 cm (3'1"–3'7") | 14" |
| 4 - 6 years | 105–120 cm (3'5"–3'11") | 16" |
| 5 - 8 years | 115–130 cm (3'9"–4'3") | 18" - 20" |
| 7 - 10 years | 125–140 cm (4'1"–4'7") | 20" - 24" |
| 9 - 12 years | 135–150 cm (4'5"–4'11") | 24" - 26" |
Note: Children's bike sizes refer to wheel diameter (in inches), not frame size. The transition to adult bikes begins at 26" wheels. Children's bikes are adjustable, saddle and handlebar heights grow with your child.
Frequently asked.
How do I measure my inseam length for bike sizing?
Stand barefoot against a wall with your feet shoulder width apart. Place a hardback book between your legs, spine up, pressed firmly against your crotch like a saddle. Mark the wall at the top of the book. Measure from floor to mark in centimetres. That number is your inseam. Do it twice to confirm.
What bike frame size do I need for my height?
Height alone is a rough guide. At 170 to 175cm, you would typically look at 53 to 55cm road frames, 42 to 45cm mountain bike frames, or 52 to 55cm hybrid frames. But torso length and arm reach matter too. The calculator gives a starting point - test riding confirms whether it actually fits you.
Should I size up or down if I'm between bike sizes?
Depends what you want. Smaller frames feel more aggressive and responsive - better for racing or sporty riding. Larger frames put you more upright with more comfort for longer distances. Neither is wrong. Think about how you actually ride rather than following generic advice.
How is children's bike size different from adult bikes?
Kids bikes size by wheel diameter - 12 inch, 16 inch, 20 inch, 24 inch - rather than frame size. Match the wheel size to your child's height and leg length. They should be able to touch the ground with both feet when seated. Kids grow fast, so do not buy too far ahead thinking they will grow into it.
Now you know your size.
Jump straight to bikes that fit you, or carry on researching. Every listing on Cyclesite shows verified frame-size data.
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