Caleb MorganBy Caleb Morgan

Updated November 2026

A bike tire size conversion chart lets you translate the same tire size written in different systems, such as 26 x 1.95 inch, 700 x 25c or 54-559 ETRTO, so you can confirm a tire fits your wheel before you order. This guide shows you how to read each sizing system, convert between them, and check the result against your rim and frame. By the end, you will be able to match a bike tire size conversion chart to your own bike with confidence.

Why Bike Tire Sizes Are Written in Different Ways

Bicycle tires have never had one universal labeling system. Different regions, bike categories and manufacturers grew up with their own conventions, so the same wheel can be labeled several ways on different tires. Road bikes often use French or metric-style numbers, mountain bikes often use inches with decimal widths, and the international ETRTO (European Tire and Rim Technical Organization) standard tries to describe the tire in millimeters so that everything can be matched precisely.

Shopping for one? See our guide: 5 Best Road Bike Shoe Size Charts (2026): Expert Picks.

The practical result is that a tire marked “26 x 1.95” and another marked “50-559” may both fit the same wheel. A conversion chart is simply a way to line these labels up side by side.

Step 1: Learn the Three Main Sizing Systems

Before you use any chart, it helps to know what each number means.

Inch Sizing (Mountain, Cruiser and Kids’ Bikes)

Inch sizing is common on mountain bikes, cruisers and kids’ bikes. A label such as 26 x 1.95 means the approximate outside diameter is 26 inches and the tire width is about 1.95 inches. Some older tires also use names like “26 x 1-3/8,” which is a different width scale, so always check whether a second number is decimal or fractional.

French and Road Sizing (700c, 700 x 23c, 700 x 28c)

Road and many hybrid bikes use the 700 designation. The “700” refers to an approximate outside diameter of about 27 inches, and the letter “c” stands for the tire width in millimeters, so 700 x 25c is a 25 mm wide tire. The “c” suffix is part of the label, not a measurement, and it is not the same as the older “C” width code some manufacturers use. Keep the 700 and the width number together when you compare labels.

ETRTO (The Most Precise System)

ETRTO labels look like 25-622 or 32-635. The first number is the tire’s width in millimeters on the rim, and the second number is the bead seat diameter in millimeters, which is the diameter where the tire’s bead sits on the rim. ETRTO is the most reliable system for matching a tire to a rim because it describes both dimensions directly.

Step 2: Use a Bike Tire Size Conversion Chart

The table below lists common tire sizes and how they line up across the three systems. It covers the sizes most riders encounter. Always confirm with the markings on your current tire or the rim’s specifications.

Inch Size French / Road Size ETRTO Typical Use
26 x 1.95 (no direct road equivalent) 50-559 Older mountain bikes, cruisers
26 x 2.1 (no direct road equivalent) 54-559 Mountain bikes
27 x 1-1/4 630 x 1-1/4 (older road) 32-630 Vintage road and touring bikes
27 x 1-1/4 (varies by brand) 32-635 Older road bikes
700 x 23c 700 x 23c 23-622 Road racing
700 x 25c 700 x 25c 25-622 Road, endurance
700 x 28c 700 x 28c 28-622 Road, gravel, touring
700 x 32c 700 x 32c 32-622 Gravel, hybrid
700 x 38c 700 x 38c 38-622 Gravel, hybrid, light trail

Note that a few inch sizes do not have an exact road equivalent, and some ETRTO numbers are shared by sizes that look different on the label. The chart is a guide for matching, not a replacement for checking the rim’s own markings.

Step 3: Check Your Rim and Frame Clearance

A conversion chart tells you whether two labels describe the same size. It does not tell you whether the tire will physically fit. Before you buy, check these points:

  1. Read the ETRTO bead seat number stamped on your rim or listed in the manufacturer’s specifications. This should match the second number of the tire’s ETRTO label.
  2. Check the rim’s recommended tire width range. Most rims list a minimum and maximum width in millimeters.
  3. Measure your current tire’s width at the widest point with the tire inflated, or use the labeled width if you trust it.
  4. Look at the frame and fork clearance. Measure the gap between the tire and the frame or fork at the closest point. Allow for mud and debris, and leave the gap larger on bikes you ride off-road.
  5. If you ride with fenders, confirm the fender accepts the new width.

For guidance on matching rims, tires and frames together, see Road Bike Rim Size Chart: How to Match Rims, Tires and Frames and 700c Bike Wheel Size Chart: How to Match Rim Size to Your Tires and Frame.

Step 4: Confirm the Size Against Your Bike Type

Once you have converted the label, check that the size makes sense for the kind of riding you do. A wide mountain bike tire on a narrow road frame will not fit, while a very narrow road tire on a gravel bike may feel unstable on loose surfaces. Use the category-specific charts when you need a closer look:

Step 5: Double-Check Before You Buy

Use this checklist before you order:

  • Wheel diameter matches (26-inch, 27-inch, 700c, 29-inch, and so on).
  • ETRTO bead seat number matches the rim.
  • Tire width sits within the rim’s recommended range.
  • Frame and fork clearance is confirmed.
  • Tube size, if you use tubes, matches the tire’s range.
  • Tire type (tubed, tubeless-ready, or tubeless) matches your rim.

A tire pressure gauge helps you set the correct pressure once the tire is on, which matters more than the exact label for ride comfort and puncture resistance. A digital gauge is easy to read at a glance.

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A set of tire levers makes mounting and removing tires much easier, especially on tighter tires with stiff beads. Choose a set made from nylon or plastic to avoid scratching the rim.

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A bead seat measuring tool is not standard, but a caliper can help you measure rim width and tire width more precisely than a ruler. A basic digital caliper gives readings in millimeters, which is what the ETRTO system uses.

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Common Mistakes

  • Matching only the diameter. A 700c tire and a 26-inch tire are different diameters, but two tires labeled with the same diameter can still have different bead seats. Always check ETRTO.
  • Ignoring the width range. A very wide tire on a narrow rim can change the profile and affect handling and pinch-flat risk.
  • Trusting the label over the rim. The rim’s own markings are the final authority.
  • Forgetting fenders and brakes. A wider tire may rub the fender, the brake caliper or the frame.
  • Mixing up “c” and inches. The “c” in 700c is part of the designation, not a width measurement in inches.

Tips for Using a Conversion Chart

  • Photograph the sidewall of your current tire before you shop. It shows the labels you need to match.
  • When in doubt, match ETRTO first. It is the most precise number on the chart.
  • Remember that tire width changes slightly with rim width and pressure, so a 25 mm tire may measure a little differently on a wide rim.
  • Keep a note of your rim’s bead seat diameter and width range in your phone for future purchases.

FAQ

What does 700 x 25c mean?

It describes a road-style tire with an approximate outside diameter of 700 mm (about 27 inches) and a width of about 25 mm. The “c” is part of the standard label and is not a unit of measurement.

Is 26 x 1.95 the same as 50-559?

Yes, these are the same tire described in two systems. The 26 in the inch label corresponds to the 559 mm bead seat in ETRTO, and 1.95 inches is roughly 50 mm wide.

Can I use a 700c tire on a 26-inch wheel?

No. The diameters are different, so the tire will not seat properly on a 26-inch rim.

How do I find my rim’s ETRTO size?

Look for the number stamped on the rim sidewall or inside the rim bed, or check the manufacturer’s specifications. It is usually given as the bead seat diameter in millimeters.

Does tire width affect speed?

Yes, but the effect depends on tire pressure, surface and rider weight. Wider tires generally roll slightly slower on smooth pavement but offer more comfort and grip.

Can I fit a wider tire than my label says?

Sometimes, if the rim and frame allow it. Check the rim’s width range and the clearance around the frame and fork before you try.

Should I consult a professional before changing tire size?

If you are unsure whether a tire fits safely, especially on a carbon rim or a bike with a specific manufacturer’s warning, ask a qualified bike mechanic or check with the frame or rim maker before riding.

Conclusion

A bike tire size conversion chart is most useful when you know which system your current tire uses and which numbers matter for fit. Start with ETRTO, confirm the rim’s width range, and check frame clearance before you buy. Once you have matched the labels, you can shop with confidence.

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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.