Caleb MorganBy Caleb Morgan

Updated November 2026

A bike frame size chart in cm matches your body measurements to a frame size, so you can narrow down bikes before you ever sit on one. This guide shows you how to measure your height and inseam, read a centimeter chart correctly, and check the fit once you have a bike in front of you. Most adults can get a reliable starting size in about ten minutes.

Why Centimeters Matter for Frame Sizing

Bike brands use different sizing systems. Some label frames S, M, and L, while others use inches or centimeters. A centimeter chart is the most precise option because it gives you a number you can compare directly across brands. The measurement that matters most is the seat tube length, which is the distance from the center of the bottom bracket (where the pedals attach) to the top of the seat tube. Keep in mind that the number on the chart describes the frame, not your body.

Shopping for one? See our guide: Trail Bike Size Chart: 3 Best Picks for Finding Your Frame Fit.

Step 1: Measure Your Height and Inseam

Start with two numbers. Stand barefoot against a wall with your heels about 15 cm apart, and mark the top of your head. Measure from the floor to the mark in centimeters. Next, measure your inseam: stand with your back against the wall, place a hardcover book between your legs, and push it up until it touches your crotch. Measure from the floor to the book’s spine. Multiply that number by 0.67 for a rough road bike reference, or use it directly on most brand charts.

Step 2: Read the Centimeter Chart

Find your height or inseam on the chart, then read across to the matching frame size. Charts are approximate, so look at the ranges, not single numbers. If you fall between two sizes, consider your riding style. Riders who want an upright position or plan to commute often lean toward the smaller frame, while those who ride fast or prefer a stretched-out posture often choose the larger one.

Rider Height (approx.) Typical Frame Size (approx.)
150–160 cm 44–48 cm
160–170 cm 48–52 cm
170–180 cm 52–56 cm
180–190 cm 56–60 cm

Step 3: Check the Fit on the Bike

A chart gets you close, but fit confirms the choice. Sit on the saddle with your pedal at the bottom of its stroke. Your knee should be slightly bent, roughly 25 to 35 degrees. When you are on the bike with your hands on the handlebar, you should have a small bend in your elbows and be able to reach the brake levers without stretching. Standing over the top tube, you should have about 2 to 5 cm of clearance on a road bike and more on a mountain bike.

Quick Fit Checklist

  1. Record your height and inseam in centimeters.
  2. Find the matching frame size range on the chart.
  3. Choose the size, adjusting for riding style.
  4. Test ride and check knee bend, reach, and standover clearance.
  5. Adjust the saddle height and handlebar stem if the frame is close.

Common Mistakes to Avoid

  • Choosing a frame based on wheel size or bike model name alone.
  • Using height only and ignoring inseam, which varies a lot between riders.
  • Assuming a centimeter size matches across brands. Always check the specific brand chart.
  • Buying online without checking the reach and stack numbers if the brand lists them.
  • Ignoring standover height, which matters for safety when you stop.

If you are unsure about your fit or have a medical condition affecting your posture, consult a professional bike fitter.

  • Tape measure or fit ruler: A flexible measuring tape helps you record height and inseam accurately. View on Amazon
  • Bike fitting guide book: A clear reference explains geometry numbers and how they affect comfort. View on Amazon

FAQ

Is a centimeter chart more accurate than S, M, and L sizing?

Yes, usually. Centimeter sizing gives you a specific number to compare across brands, while S, M, and L labels vary by manufacturer. Always confirm the seat tube length on the brand’s own chart.

Should I size my bike by height or inseam?

Use both if you can. Inseam is often more reliable for the frame, while height helps confirm the overall size. If the two suggest different sizes, test ride both if possible.

Can I adjust a bike that is slightly the wrong size?

Small changes are possible through saddle height, saddle fore-aft position, and stem length. A frame that is far too large or too small cannot be fixed with adjustments, so choose the right size first.

Conclusion

A bike frame size chart in cm gives you a precise starting point using your height and inseam. Measure carefully, read the brand’s chart, and confirm the fit with knee bend, reach, and standover clearance. Once the numbers and the ride feel right, you are ready to buy with confidence.

Ready to choose one?

Caleb Morgan

About Caleb Morgan

Caleb Morgan is part of our editorial team and reviews and edits our cycling for beginners guides, checking product details against manufacturer specifications and owner feedback.