Caleb MorganBy Caleb Morgan

Updated November 2026

A bike tire inner tube size chart tells you which tube fits your tire, and it works by matching two numbers: the tire’s width and the wheel’s diameter. Once you read the size printed on your tire sidewall and find it on the chart, you’ll know exactly which tube to buy. This guide walks you through that process in five practical steps so you don’t end up with a tube that’s too small, too large, or the wrong valve length.

Step 1: Read the Size on Your Tire Sidewall

Look at the tire’s sidewall for printed numbers. You’ll usually see a format like 27 x 1-1/4, 700 x 25c, or 26 x 2.10. The first number is the approximate outside diameter, and the second is the tire width. Some tires also show an ETRTO code such as 37-584, where the first number is the tire width in millimeters and the second is the bead seat diameter in millimeters. Write down whichever format your tire uses.

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

Step 2: Match the Size to a Tube Chart Entry

Find your tire size on a size chart. Tubes are usually listed in both inch and metric formats, so you may need to convert. The most common formats you’ll see are:

Tire Designation ETRTO Typical Use
26 x 1.75 – 2.125 47-559 to 57-559 Mountain bikes, older cruisers
27 x 1-1/4 32-630 Older road and touring bikes
700 x 25c 25-622 Road bikes
700 x 38c 38-622 Gravel and hybrid bikes
20 x 1.75 – 2.125 47-406 to 57-406 BMX and kids’ bikes

If your tire is labeled in inches only, check the metric equivalent before buying. A tube meant for a 26-inch wheel is not interchangeable with a 27-inch tube, even though the numbers look close.

Step 3: Confirm the Valve Type and Length

The tube size chart only covers diameter and width. You also need the right valve. Most bikes use one of three types:

  • Schrader (American): thick valve, same as a car tire, common on mountain and hybrid bikes.
  • Presta (French): thin valve with a locking nut, common on road and gravel bikes.
  • Dunlop (Woods): thin valve without a locking nut, found on some older and European-style bikes.

Valve length matters too. Deep-section rims need a longer valve stem so you can reach the pump head. Check your rim depth before you buy, or measure the stem you’re replacing.

Step 4: Check Your Rim Width and Tire Fit

A tube sized correctly for the tire can still cause problems if the rim is too narrow or too wide for the tire. Manufacturers usually publish an acceptable width range for each tire, and it’s worth checking it. For more detail on rim fit, see Road Bike Rim Size Chart: How to Match Rims, Tires and Frames and Mountain Bike Rim Width Tire Size Chart: Match Tires to Your Rims (2026).

Wider tires also need the right tube. A tube labeled for a narrower range can stretch too thin or fold inside a wider tire, which leads to pinch flats. If you’re unsure, pick the tube that lists your exact tire width rather than a range that just overlaps.

Step 5: Buy the Tube and Install It Correctly

Once you have the right tube, install it with care. Inflate it slightly before seating it so it takes its shape, and push the valve through the rim hole first. Work the tire bead back onto the rim by hand, starting opposite the valve. Inflate gradually and check that no tube is pinched along the bead. The right size is only half the job; careful installation prevents most early flats.

Common Mistakes

  • Matching on wheel size alone and ignoring the tire width.
  • Buying a Schrader tube for a Presta rim, or the reverse.
  • Choosing a valve that is too short for a deep rim.
  • Inflating a tube past the maximum pressure printed on the tire.
  • Skipping the sidewall check and relying on memory for your tire size.

A tire lever set makes removing and seating tires much easier and reduces the risk of pinching the tube. Search for plastic tire levers for bike tubes View on Amazon.

A compact floor pump with a pressure gauge helps you inflate to the correct pressure without guessing. Search for bike floor pump with pressure gauge View on Amazon.

FAQ

Can I use a tube one size bigger than my tire?

Not recommended. An oversized tube can bunch up inside the tire and cause blowouts or pinch flats. Stick to the size printed for your tire.

Do I need a new tube every time I fix a flat?

Not always. Small punctures can be patched, but a tube with a torn valve, a long gash or multiple leaks is best replaced. For more on sizing, see Bike Tube Size Chart: How to Match Your Inner Tube in 5 Steps.

What if my tire size isn’t on the chart?

Measure the tire’s bead seat diameter and width, or check the manufacturer’s specifications. If you’re unsure, take the tire to a local bike shop for confirmation before buying.

Conclusion

A bike tire inner tube size chart makes tube selection simple once you know your tire’s width, wheel diameter, and valve type. Match those three details carefully, and the right tube will seat cleanly and hold air. When in doubt, compare your sidewall markings against the chart before you buy.

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.