You may find both units in the description of the bike.
18 inch frame bike size height.
The deciding factor for the size of a bicycle is the frame in particular the seat post the distance from the center of the bottom bracket to the top of the seat post.
Bike frame sizes are measured in the same way for all styles of bicycle.
To measure your bike s frame size take a measuring tape and place the tape in the center bolt of your bike s cranks.
The sizes are measured in inches mtb or centimeters.
5 7 5 10 170 178cm.
147 155 cm 4 9 5 1 153 162 cm 5 2 5 3 8.
161 172 cm 5 3 4 5 7 7 170 179 cm 5 6 9 5 10 5 177 188 cm 5 9 7 6 2 186 196 cm 6 1 2 6 5 2 195 203 cm 6 4 6 7 9.
Bike frame size chart.
The calculation here will give you your bike s frame size.
If it is just the frame this will be the center point in the bottom bracket shell.
Dialing in your fit.
In very general terms an 18 inch bicycle is best for someone just under six feet in height but factors like inseam length and the differences between bike manufacturers can all influence the fit.
Height cm frame size inches.