What Are 700x40c Tire Size In Inches?

Bike tires with a ‘c’ in their dimensions belong to the French sizing system, one of the biking industry’s most common measurement standards. This is in addition to the ISO, English, and other measurement systems all around the world. 

But unless you are a biker or work in the bike industry, stamps such as 700x45c in inches on the tires may not make a lot of sense to you. If you’re curious about the numbers on your bike tires and what they could possibly mean, here is the answer. 

700x40c Tire Size In Inches

700x40c Tire Size In Inches

There is nothing too much to say. The question is simple, the answer is simple too. 700x40c Tire Size In Inches are:

700 = 27.5 inches
40mm = 1.57 inches

Where Are 700x45c Written On The Tires?

In most road bikes, numbers such as 700x45c in inches are written/stamped on the sidewall of the tires. 

The number 700 comes from the fact that nearly all types of bikes in existence have an outer diameter of about 700 millimeters. Since the first bicycle/bike was invented in 1817 and further development, all the tires of these bikes were available in four variations, which were 700 – A, B, C, and D.  

Back then, cyclists chose the variation of the bike depending on whether they wanted to go for a casual ride race or train on the dirt tracks. Although this was not the most convenient, swapping the tires was relatively easy since the road brake calipers were wider in the older bikes. 

However, 700A, 700B, and 700D were not as popular among cyclists, and eventually, manufacturers stopped making them. Only 700C was preferred by the cyclists, which gradually became the standard for modern track and road bikes. 

In general, 700C is a cycling industry measurement, which refers to tires, wheels, and rims with a 622 millimeter of BSD or bead seat diameter. 

Note: In the French sizing system, bike tires are still denoted using the letters ‘a, ‘b,’ ‘c,’ and ‘d’. Bike tires with ‘a’ are usually the thinnest, while those with ‘d’ are the thickest and are measured in millimeters. Most modern bike manufacturers generally drop the letters while stamping the bike tires with their dimensions. 

However, unless the tire measurement is marked in inches, which is usually the case with ISO/European sizing system, bike tires with no letters in their dimensions are understood as belonging to the French sizing system. 

So What Does It Mean If A Bike Tire Has 700x45c Written On It?

The 700 refers to the nominal diameter of the bike tire, while the 45 refers to the width of the bike tire. The letter ‘c’ is a width code used in the French sizing system, especially in the olden days. This coding in bike tires means ‘a’ is not as narrow as a tire marked ‘b’ but is narrower than another one with a ‘d’ on it. 

Until a few years ago, 700c bike tires were mostly a feature that was common in hybrid and gravel bikes and very rarely on track and road bikes. But you will see 650b wheels on these bikes, especially in the newer ones.

In addition, most manufacturers make road bike tires with a 700c measurement, which you can easily swap with gravel or hybrid bikes with a 650b measurement if you wish. 

Is 700x45c In Millimeters The Same As The One In Inches? 

Not exactly. This is because the French sizing system measures the tires in millimeters, while the ISO, which is the international standard in most countries, measures the tires in inches. In addition, bike tire measurement tends to vary from country to country. 

Therefore, 700x45c in inches is very different from one written in millimeters. In addition, two bike tires that are measured in inches can have different sizes. For instance, a bike tire with 1.75 inches is usually different from one that says 1 ¾ inch.

Using the wrong sized tire on your bike comes with several disadvantages, including discomfort while riding, tire being punctured more easily, and of course, the compromise on the overall performance. 

How Do I Pick The Right Tire For My Bike?

For picking the right tires for your bikes, a rule of thumb is to check the dimension of the old tire. The sidewall of the bike tire is where you will find the dimensions stamped by the manufacturers, so that is where you should look.

Additionally, while getting new bike tires, make sure they have the same dimensions as the old ones. Getting the right bike tires is essential as it can determine the overall performance as well as comfort. Fitting your bike with the right tires will also prevent it from puncturing easily and will, therefore, last longer. 

It’s the same as fitting the bike with the right inner size tube. For instance, when you want to replace inner tubing, you ask and wonder what size inner tube for 26 x 1.95 would be a perfect fit for your bike tires that measure 26 inches. 

For picking the best bike tires, here are a few pointers

Look at the tread patterns that are open along the tires’ sides but are tightly packed with rubber lugs towards the center of the tire. 

The open tread pattern on the edges allows the tire to have a solid grip irrespective of the surfaces – gravel or dirt. In addition, the tight pattern at the center is fantastic for riding on paved and other similar surfaces. 


Although the simple answer to 700x45c in inches translates to 27.5 inches and 1.77 inches, choosing a tire for your bike is not as straightforward. Bike tires, whether MTB, gravel, or road bikes, have different measurement standards, which can make it tricky to pick the right fit. 

Beginners looking for the perfect tire for their bikes can find it even harder because tires measured in inches can also be different in actual sizes, as we’ve mentioned above. 

Regardless of the sizes and what measurements are written on your bike tires, if you’re looking to change them, pick the tire with the exact designations written on the old ones. If you want to change other bike components, including the inner tubes, the same tip also works great. 

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