Bicycle tyres and inner tube sizes

It’s easy to get confused by the bewildering variety of bicycle tyre and inner tube size naming systems.

To clear up the confusion, the ISO standard sizes were introduced. However, you may still come across many different numeration formats.

A conversion table below may come in handy the next time you go shopping for new tyres or inner tubes for your bike.

ISO	Imperial	Metric	American	Tyre diameter (mm)	Tyre circumference
40-635	28 x 1 ½	700B		715	2.25
25-630	27 x 1		27 x 1 1/8	680	2.14
32-630	27 x 1 ¼		27 x 1 3/8	694	2.18
18-622		700 x 18C	700 x 20C	658	2.07
23-622		700 x 23C	700 x 23C	668	2.10
25-622		700 x 25C	700 x 25C	672	2.11
28-622	28 x 1 5/8 x 1 1/8	700 x 28C	700 x 28C	678	2.13
32-622	28 x 1 5/8 x 1 1/4	700 x 32C	700 x 35C	686	2.16
37-622	28 x 1 5/8 x 1 3/8	700 x 35C		696	2.19
47-622		700 x 47C		716	2.25
32-597	26 x 1 ¼			661	2.08
28-590		650 x 28A		646	2.03
37-590		650A		664	2.09
28-584		650 x 28B		640	2.01
40-584	26 x 1 ½	650B		664	2.09
20-571			26 x ¾	611	1.92
23-571			26 x 1	617	1.94
40-571		650C		651	2.05
25-559			26 x 1.0	609	1.91
32-559			26 x 1.25	623	1.96
40-559			26 x 1.5	639	2.01
47-559			26 x 1.75	653	2.05
50-559			26 x 1.9	659	2.07
57-559			26 x 2.125	673	2.11
28-541		600 x 28A		597	1.88
37-541		600 x 35A		615	1.93
32-540	24 x 1 3/8			604	1.90
28-520			24 x 1 1/8	576	1.81
37-507			24 x 1.5	581	1.83
47-507			24 x 1.75	601	1.89
37-501	22 x 1 3/8			575	1.81
37-489		22 x 1 3/8		563	1.77
28-451	20 x 1 1/8			507	1.59
35-451	20 x 1 3/8			521	1.64
28-440		500 x 28A		496	1.56
32-440		500A		504	1.58
28-406			20 x 1/8	462	1.45
37-406			20 x 1.5	480	1.51
47-406			20 x 1.75	500	1.57
54-406			20 x 2.0	514	1.61
32-369	17 x 1 ¼			433	1.36
28-355			18 x	411	1.29
40-355			18 x 1.5	435	1.37
47-355			18 x 1.75	449	1.41
37-349	16 x 1 3/8			423	1.33
32-340		400A		404	1.27
37-340		400 x 35A		414	1.30
47-305			16 x 1.75 x 2	399	1.25
47-203			12 x 1.75	297	0.93

Did you know?

1. When you are choosing the inner tubes for your tyres, remember that besides the diameter, tyre width is another factor to consider. There are different tyre widths in mountain bikes, road bikes, touring bikes and children’s bikes.

2. There are two popular types of the inner tube valves: Presta and Schrader.

Knowing your size is vital when you shop for clothes....

693

If you have ever been shopping for shoes in Continental...

841

The UK shoe sizing system has developed with an Anglo-Saxon...

737

Are you planning a shopping spree in Paris? Or maybe...

654

When we watch sports from a high angle view camera...

707

Over time, there have been many conventions of paper...