Bike Size Calculator
Find the right bike frame size from your height and inseam. Choose road, mountain, hybrid or kids bikes to get the size label (XS–XXL), frame size in centimeters and inches, a saddle height starting point and the standover clearance to look for.
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Floor to crotch, barefoot. Leave empty to estimate.
Floor to crotch, barefoot. Leave empty to estimate.
How to use the Bike Size Calculator
- Pick the bike type: road/gravel, mountain, hybrid/city or kids.
- Enter your height in feet and inches or centimeters.
- Measure your inseam: stand barefoot against a wall with a book pressed up between your legs and measure from the floor to the top of the book.
- Press Find my size to see the size label, frame size and saddle height.
- Compare with the brand chart and test ride, especially if you are between sizes.
Bike size formulas
- Road / gravel: frame size (cm) = inseam (cm) × 0.70
- Mountain and hybrid: frame size = inseam (cm) × 0.685 − 10 cm, usually quoted in inches (÷ 2.54)
- Saddle height: inseam × 0.883, from the bottom bracket centre to the top of the saddle
- Standover: about 2.5–5 cm (1–2 in) clearance on road bikes and 5–10 cm (2–4 in) on mountain bikes
Example: 175 cm tall with an 81 cm inseam → road 81 × 0.70 = 56.7 cm (size L/M border), mountain 81 × 0.685 − 10.2 = 45.3 cm ≈ 17.8 in (M).
Bike size chart by height
| Rider height | Road (cm) | Mountain (in) | Size |
|---|---|---|---|
| 4′11″–5′3″ (150–160 cm) | 47–50 | 13–14 | XS |
| 5′3″–5′6″ (160–167 cm) | 51–53 | 15–16 | S |
| 5′6″–5′9″ (167–175 cm) | 54–55 | 17–18 | M |
| 5′9″–6′0″ (175–183 cm) | 56–58 | 19–20 | L |
| 6′0″–6′3″ (183–190 cm) | 58–60 | 21–22 | XL |
| 6′3″+ (190+ cm) | 61–63 | 23+ | XXL |
Kids bike sizes
| Wheel size | Child height | Inseam | Typical age |
|---|---|---|---|
| 12″ | 2′9″–3′3″ (85–100 cm) | 14–17 in (35–42 cm) | 2–4 |
| 14″ | 3′1″–3′7″ (95–110 cm) | 16–19 in (40–48 cm) | 3–5 |
| 16″ | 3′5″–3′11″ (105–120 cm) | 18–22 in (45–55 cm) | 4–6 |
| 20″ | 3′9″–4′5″ (115–135 cm) | 20–24 in (50–62 cm) | 6–9 |
| 24″ | 4′3″–4′11″ (130–150 cm) | 24–28 in (60–72 cm) | 8–12 |
| 26″ / adult XS | 4′9″+ (145+ cm) | 26+ in (66+ cm) | 11+ |
These charts are typical ranges. Every brand's geometry differs, so use the manufacturer's chart for the final choice.
Frequently asked questions
How do I calculate my bike frame size?
A common rule for road bikes is inseam (cm) × 0.70 for the seat tube length; for mountain bikes inseam × 0.685 then subtract about 10 cm (4 in). With an 81 cm inseam: road 56.7 cm, mountain 45.5 cm (about 18 in, a medium).
What size bike do I need for my height?
Roughly: road bikes, 5′3″–5′6″ ride 51–53 cm (S), 5′6″–5′9″ ride 54–55 cm (M) and 5′9″–6′0″ ride 56–58 cm (L). Mountain bikes, 5′6″–5′10″ usually ride a medium 17–18 in frame. Brand charts vary, so check the specific model.
Why are road bikes sized in cm and mountain bikes in inches?
It is tradition: road frames are usually labelled by seat tube length in centimeters, while mountain bikes used inches. Today many brands of both types simply use XS–XL labels, and the geometry (reach and stack) matters more than the number.
What if I am between two sizes?
Riders with longer legs and a shorter torso often prefer the larger frame; a longer torso suits the smaller frame with a longer stem. If you want a more upright, nimble ride choose the smaller size; for stability and stretch choose the larger one.
How do I size a kids bike?
Kids bikes go by wheel size, not frame size: about 12 in wheels for 2–4 year olds, 14–16 in for 3–6, 20 in for 6–9, 24 in for 8–12 and 26 in or adult XS for older children. The child should be able to stand over the top tube and touch the ground with the balls of both feet.
How high should my saddle be?
A good starting point is inseam × 0.883, measured from the centre of the bottom bracket to the top of the saddle (the LeMond method). At the bottom of the pedal stroke your knee should still be slightly bent.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.