the box must match exactly. the second number on the tube box will be a range, like 1.8-2.3 or 19-26. your tire width must be within that range for the tube to fit.
once you have that measured, use the chart below as a guide to select the best size bike for you. if your measurements fall between two sizes on the chart above, there’s no need to worry. going for the larger size is recommended because you can then adjust the seat to find perfect fit for you. 