Bicycles are measured in several different ways. Bicycle Business provides the following a cycle sizing guideline, however it may not take into account personal health, wellbeing, flexibility, personal motion or riding tendencies.
What is Inseam?
The most important factor in getting the right frame is measuring your Inseam (Inside Leg Length) - a distance from the floor to your crotch.
How to measure your inseam?
Incorrectly measuring may lead to the wrong frame size. Bicycle Business recommends that for the most accurate inseam measurement you are to:
Wear minimal clothing preferably underwear or lycra. Avoid wearing baggy pants or jeans when measuring as this will affect the final inseam measurement.
Place a straight edge between your legs and firmly against your crutch (suggest using a book or level), but remember it has to be completely horizontal.
Measure the distance from the top of the spirit level (or the book) to the ground.
Mark this height in comparison to the wall
Measure the height from the floor to the mark
If having problems ask somebody for help. For accuracy, repeat the measurement several times and calculate the average.