The quick answer
To choose a tube, you need three things: the diameter of your wheel, the width of your tire, and the valve type your rim takes. All of these start with the markings on the tire’s sidewall. The diameter has to match exactly. The width usually only has to fall within the range printed on the tube’s box. Then check the valve type and, for deeper rims, valve length.
Step 1: Read the size on your tire
The size is printed on the sidewall of the tire. You will usually see one of these formats:
- Inch sizes: for example 26 x 1.95. The first number is the nominal wheel diameter in inches and the second is the tire width in inches.
- French or metric sizes: for example 700 x 28c, where 700 is the nominal diameter in millimeters and 28 is the width in millimeters. The letter at the end comes from an old French sizing system and is not something you need to match against the tube.
- ETRTO (ISO) sizes: for example 50-559. The first number is the tire width in millimeters, and the second is the bead seat diameter in millimeters. This is the most reliable number to match.
Some tires show more than one format. If the sidewall is hard to read, check the rim or see our guide to reading bike tire anatomy, which explains where size markings appear and what they mean.
Step 2: Match the diameter
Diameter has to match. A tube made for a different bead seat diameter will not fit properly. Common wheel sizes include 16, 20, 24 and 26 inch wheels, 27.5 inch (also called 650B), 29 inch and 700c.
An important detail: 700c road wheels and 29 inch mountain bike wheels share the same bead seat diameter, 622 mm. Their tires differ in width, but in principle tubes marked for that diameter can be matched by width range. Do not assume other similar-sounding sizes are interchangeable, for example 26 inch and 27.5 inch, or the several different 26 inch standards that exist. When in doubt, use the ETRTO number, and check the bike tire size chart for bead seat diameters.
Step 3: Check the width range
Inner tubes stretch, so they are sold for a range of tire widths rather than one exact width. A tube labeled 26 x 1.75-2.125, for example, is designed for a 26 inch wheel with a tire in that width range.
So, do bike tubes need to be an exact size? For diameter, yes. For width, no, as long as your tire width falls inside the range the manufacturer states. Staying near the middle of the range is generally better than at the extreme edges.
Common sizes
Sizes vary by region and age of the bike, but you may see:
- Road and gravel: 700c tubes in narrower or wider ranges, such as for 23-32 mm or 28-40 mm tires.
- Mountain bikes: 26, 27.5 and 29 inch tubes for 1.9 to 2.5 inch or wider tires, with plus and fat bike tubes for wider tires still.
- Kids and compact bikes: 12, 16, 18, 20 and 24 inch tubes.
These are examples, not a complete list. Always check the actual numbers on your tire.
Step 4: Choose valve type and length
Tubes come with different valves, and the one you need depends on the hole in your rim:
- Presta: a slim valve, common on road bikes and many performance bikes.
- Schrader: a wider valve like those on car tires, common on kids bikes, commuters and many mountain bikes.
- Dunlop (Woods): found on some city bikes in certain regions, and less common elsewhere.
Our guide to Presta and Schrader valve types shows how to tell them apart. A tube’s valve has to suit the rim hole. A Presta tube in a larger Schrader hole can rattle around, and a Schrader valve will not fit through a narrow Presta-sized hole.
Valve length matters too. Deeper rims need longer valves so the pump head can attach to the valve above the rim. Check your rim depth and choose a stem length that clears it, and where a removable valve core is offered, check whether that is useful for adding sealant or extenders.
Tube material and extras
- Butyl rubber: the common, economical choice that holds air reasonably well.
- Latex: lighter and often more supple, but typically loses air faster and needs more frequent inflation.
- Lightweight or TPU tubes: very light, often at a higher price, and compatibility with your rim and tire should be confirmed.
- Thicker or puncture-resistant tubes: more weight, more protection.
- Self-sealing tubes: include sealant inside to close small punctures. They are not a guarantee against flats.
What if the tube is the wrong size?
A tube that is too large for the tire can bunch up or fold inside and may be pinched or punctured. A tube that is too small has to stretch, which thins the wall and can make it fail sooner. A tube with the wrong diameter will not fit at all. It is better to buy the correct tube than to force a close match. A mismatched tube is one reason a tire can keep going flat; see why your bike tire keeps going flat.
Checklist before you buy
- Read the size from the sidewall, including the ETRTO number if present.
- Match the wheel diameter exactly.
- Confirm your tire width sits within the tube’s range.
- Check valve type and the hole size in your rim.
- Pick a valve length that clears your rim depth.
- Carry a spare tube and a pump, along with a way to patch tubes.
Frequently asked questions
How do I know my bike tube size?
Read the numbers on your tire sidewall and look for a tube with the same diameter and a width range that includes your tire width.
What are the common sizes of bicycle tubes?
They range from small kids sizes up to 29 inch and 700c, with width ranges printed on each box. Sizes vary widely, so match to your tire rather than a general list.
Can I use a 700c tube in a 29 inch tire?
They share a 622 mm bead seat diameter, so in many cases yes, provided the tube’s width range covers your tire. Check the tube’s labeling to be sure.