Before buying, if you have questions about your bicycle wheel size and cannot find a suitable model, please don't worry; this article will answer how to determine your wheel size.
1.CHECK PURCHASE INFORMATION
you buy online: View the bicycle details on the retailer's website; there will be a "Specifications" section where the specific wheel size will be written.

If you buy in the store: The wheel size is usually in the specification manual that comes with the bike; if not, you can ask the seller.
2.CHECK THE TIRE MARKINGS
Most bicycle tires are marked with the wheel size on the side.
There are three standard tire markings:
2.1 International size standards:
European Tyre and Rim Technical Organisation (ETRTO) European Tyre and Rim Technical Organization established standards for tires and rims. The well-known International Organization for Standardization (ISO) has also followed this set of criteria. The code will consist of 5 digits in the form of XX-XXX. The first two digits indicate the width of the wheel in millimeters. The last three digits represent the inner diameter of the tire, 40-622. 40 refers to the width of the tire after inflation is 40mm. Six hundred twenty-two means that the inner diameter of the rim is approximately 622mm.
2.2 French sizes:
The second half of the model 700*38c is the name of the older generation. 700 refers to the outer diameter of the inflated tire, approximately 700mm, and 38 refers to the excessive width of the tire, 38mm.
2.3 Traditional inch size:
Generally used on mountain bikes and commuter vehicles. Example: 28 x 1 5/8 x 1 3/828 means that the outer diameter of the inflated tire is approximately 28 inches (1 inch is about 25.4 mm, about 711mm). 1 5/8 refers to the tire thickness after inflation (this number can be omitted). 1 3/8 refers to the tire width after inflation is 1 3/8 inches. Because the tire thickness can be forgotten after inflating, the numbers have commonly seen are 26x2.0, 26x2.25, etc.