700c and 29-Inch Bicycle Tires: Sizes, Markings and Real Differences

Yes. A 29-inch wheel and a 700c wheel use the same rim diameter. Both are built around a 622 mm bead seat diameter, and the ETRTO/ISO code ends in "-622" for both. "700c" is the traditional road and touring label. "29-inch" (or "29er") is the mountain bike label for the same rim with a wider tire. The labels mostly tell you what kind of tire to expect, not a different rim size. The sidewall numbers explain why.

Is a 29-inch wheel the same as 700c?

A 29-inch wheel and a 700c wheel share the same 622 mm bead seat diameter. A 29 x 2.25 in mountain bike tire and a 700 x 28c road tire can therefore mount on rims of the same diameter. Whether a particular rim width and frame can take that tire is a separate question.

The two names come from different labelling traditions:

• 700c comes from the French system. "700" was the approximate overall tire diameter in millimetres. The letter "c" identified a rim diameter class, not a width.
• 29-inch is a nominal wheel size. It describes the rough outside diameter of a 622 mm rim fitted with a wide mountain bike tire, which comes out near 29 inches.

Neither name is a precise measurement. The reliable number is the bead seat diameter, 622 mm.

How to read the numbers on the tire sidewall

A bicycle tire sidewall usually shows one or more size markings plus some performance information. Only the size markings tell you about rim compatibility. The most precise one is the ETRTO marking.

ETRTO size marking: width and bead seat diameter

The ETRTO marking gives two numbers in millimetres, written as width-diameter, for example 28-622 or 57-622. The system was developed by the European Tyre and Rim Technical Organisation and is also used in ISO 5775.

• First number (28, 57): the nominal tire width in millimetres.
• Second number (622): the bead seat diameter in millimetres. This is the diameter of the rim surface where the tire bead sits.

If two tires both end in -622, they are designed for rims of the same diameter, whatever their other labels say. You may also see the format reversed, such as 622x28. The numbers mean the same thing.

French marking: 700 x 28c

A marking such as 700 x 28c or 700x28C combines a nominal size (700) with a nominal width in millimetres (28). The letter "c" is a leftover from the old French rim diameter classes, not a width. Every 700c tire, from 700 x 23c to 700 x 45c, is meant for a 622 mm rim.

The "700" stays the same even when the real overall diameter changes. A narrow 700 x 23c tire is noticeably smaller in outside diameter than a 700 x 45c tire, yet both carry the same "700".

Inch marking: 29 x 2.25

A marking such as 29 x 2.25 gives a nominal wheel size in inches (29) and a nominal tire width in inches (2.25). The 2.25 in width is about 57 mm, so the tire usually also shows 57-622.

Decimal inch sizes like 29 x 2.25 are a different style from fractional sizes like 28 x 1-5/8 x 1-3/8. Fractional sizes do not always map to the same rim. Always check the ETRTO number when it is available.

Markings that are not dimensions

Several sidewall markings describe performance or construction, not size. They do not affect whether a tire fits a 622 mm rim.

• Pressure range, in psi and/or bar (for example, 50–80 psi). This is the manufacturer's allowed inflation range. Stay within it, and also within any limit printed on the rim.
• TPI (threads per inch). This describes how dense the casing fabric is, not the tire size.
• Tubeless or tubeless-ready labels. These say whether the tire is designed to be used without an inner tube on a compatible rim.
• E-bike ratings, such as markings for e-bike use up to a stated speed in km/h. These indicate the tire is approved for that use, not a different size.
• Direction arrows and bead type (wire or folding). These cover mounting direction and construction.

What size is a 700c bike tire?

A 700c bike tire fits a rim with a 622 mm bead seat diameter. Its width is the second number in the 700 x __c marking, in millimetres. The ETRTO code puts that same width first: 700 x 32c is normally 32-622.

"700c" covers a wide range of widths. The table below shows how common labels relate to the ETRTO code. The usage column is a general guide only.

Common label	ETRTO marking	Nominal width	Typical use
700 x 23c	23-622	23 mm	Narrow road
700 x 25c	25-622	25 mm	Road
700 x 28c	28-622	28 mm	Road, endurance, commuting
700 x 32c	32-622	32 mm	Commuting, light gravel
700 x 40c	40-622	40 mm	Gravel, touring, hybrid
700 x 45c	45-622	45 mm	Gravel, trekking
29 x 2.1	54-622	about 54 mm	Cross-country mountain bike
29 x 2.25	57-622	about 57 mm	Trail mountain bike
29 x 2.4	about 61-622	about 61 mm	Trail and enduro mountain bike

There is no fixed point where a 700c tire becomes a 29-inch tire. The two ranges overlap. Wide gravel tires are sometimes sold in both styles, such as 700 x 50c or 29 x 2.0. Both are 622 mm tires.

Is 622 the same as 700c?

Yes. In current bicycle tire sizing, 622 and 700c refer to the same rim diameter. "622" is the measured bead seat diameter in millimetres. "700c" is the traditional nominal name for tires that fit that rim.

The bead seat diameter is the number that decides whether a tire can physically seat on a rim. The tire bead must match the rim's bead seat diameter. A tire marked -622 belongs on a rim marked 622, often written as 622 x 19 or 622x25. In these rim markings, the second number is the rim's inner width in millimetres. Many European tires are also labelled "28-inch" for the same 622 mm rim.

One caution: an older marking such as 28 x 1-1/2 refers to a 635 mm bead seat diameter. That is a different rim and is not interchangeable with 622 mm. Check the ETRTO number when a tire carries only an inch marking.

How tire width affects sidewall height, overall diameter and circumference

On the same 622 mm rim, a wider tire is generally also taller. That makes the overall wheel diameter and circumference larger. This is why a 29-inch mountain bike tire is bigger on the outside than a 700 x 25c road tire, even though both fit the same rim diameter.

The aspect ratio on bicycle tires

Bicycle tires usually do not print an aspect ratio the way car tires do, where 55 means sidewall height is 55% of width. For a rough calculation, you can assume the tire's height above the rim is close to its width. Real tires are often somewhat less tall than they are wide. The actual ratio varies with tire design, casing, pressure and rim width.

Steps to estimate overall diameter and circumference

1. Start with the bead seat diameter: 622 mm.
2. Estimate tire height from the nominal width. Using the simple 1:1 assumption, a 28 mm tire has a height of about 28 mm.
3. Add the tire height twice, once for the top of the wheel and once for the bottom: 622 + 2 x 28 = 678 mm overall diameter.
4. Multiply the diameter by π (about 3.1416) to estimate circumference: 678 x 3.1416 ≈ 2130 mm.
5. To convert the diameter to inches, divide by 25.4: 678 / 25.4 ≈ 26.7 in.

Calculated comparison of 622 mm tire sizes

The values below use the simple assumption that tire height equals nominal width. They are geometric estimates, not measured dimensions.

Tire	Nominal width	Estimated overall diameter	Estimated circumference	Diameter in inches
23-622 (700 x 23c)	23 mm	668 mm	about 2099 mm	about 26.3 in
25-622 (700 x 25c)	25 mm	672 mm	about 2111 mm	about 26.5 in
28-622 (700 x 28c)	28 mm	678 mm	about 2130 mm	about 26.7 in
40-622 (700 x 40c)	40 mm	702 mm	about 2205 mm	about 27.6 in
56-622 (29 x 2.2)	56 mm	734 mm	about 2306 mm	about 28.9 in
61-622 (29 x 2.4)	61 mm	744 mm	about 2337 mm	about 29.3 in

The table shows where the name "29-inch" comes from. Only with a mountain-bike-width tire does a 622 mm wheel reach roughly 29 inches across. A typical 700c road tire on the same rim is closer to 26–27 inches in overall diameter.

In practical terms, going from a 25-622 to a 56-622 tire adds about 31 mm to the radius, which raises the axle by that amount relative to the ground. It also adds roughly 195 mm to each wheel revolution in this estimate. A bike computer set for one size will read differently with the other.

Calculated geometry versus actual tire dimensions

Calculated diameters are only a starting point. The actual size of a mounted tire can differ from its nominal marking for several reasons:

• Rim inner width: the same tire usually measures wider on a wider rim and narrower on a narrower rim.
• Tire construction and tread: casing shape, tread depth and knob height change both width and height. Two tires with the same marking from different brands may not measure the same.
• Inflation pressure: tires can grow slightly at higher pressure, and some stretch a little after mounting.
• Load: under a rider's weight the tire compresses. The rolling circumference is slightly smaller than the unloaded calculation.

For speedometer setup or precise clearance checks, measure the mounted, inflated tire. A common method is a roll-out test: mark the tire and the floor, roll the wheel one full revolution with the rider seated, and measure the distance.

Where 700c and 29-inch tires differ in practice

A 700c tire and a 29-inch tire share the 622 mm rim diameter, but they are not automatically interchangeable on a given bike. The differences come from width, rim width and frame clearance, not from the bead seat diameter.

Rim width compatibility

Rim compatibility depends on both the bead seat diameter and the rim's inner width. A narrow road rim, such as 622 x 15, may not safely support a 2.4 in mountain bike tire. A wide mountain bike rim may be unsuitable for a 23 mm road tire. Tire and rim manufacturers publish recommended width ranges, and ETRTO guidelines cover tire-to-rim width combinations. Check those recommendations, along with any tubeless or hookless rim requirements, before mixing widths.

Frame, fork and brake clearance

A larger overall diameter and width need more space in the frame and fork. A road frame built for 700 x 28c tires usually lacks room for 29 x 2.2 tires, even though the rims are the same diameter. Rim brakes add another limit: caliper or cantilever brakes have their own tire clearance. Matching bead seat diameters says nothing about whether a tire fits a particular bike. Clearance has to be checked on the frame itself.

Inner tubes

Inner tubes are also sized by bead seat diameter and a width range, for example 700 x 18–25c or 29 x 1.9–2.35. Both styles fit 622 mm rims. Choose a tube whose width range covers your tire. Make sure the valve type and length suit the rim.

Sizes often confused with 700c and 29-inch

The safest way to avoid buying the wrong tire is to compare the bead seat diameter in the ETRTO marking. Inch names in particular have been reused for different rims.

Common name	Bead seat diameter	Same rim as 700c / 29-inch?
700c, 29-inch, 29er, 28-inch (most modern European labels)	622 mm	Yes
28 x 1-1/2 (older roadster size)	635 mm	No
650b, 27.5-inch	584 mm	No
27-inch (older road size, such as 27 x 1-1/4)	630 mm	No
26-inch (mountain bike)	559 mm	No

In short: if the sidewall says -622, the tire is a 700c / 29-inch size, and the width number tells you how big it is. Whether it fits your bike depends on rim width and frame clearance, which the size marking cannot tell you.