Online Bike Sizing
Frame size is the most important consideration when buying a bike in a mens frame style. When you factor in your trunk to leg length ratio, it can make buying a bike a bit tricky size wise especially if you are buying a bike online.
A lot of manufacturers have gone to listing bike sizes as SM, MD, LG, etc. Unfortunately, that way of sizing isn't satisfactory for your online shopping needs.
You can get a more accurate approximation by using the Stand Over Height figures from Size Guide charts.
Stand Over Height Calculator
Put on a pair of shoes that are approximately the kind you wear when riding.
Place a book between your legs (all the way up) with the binding side up and and parallel to the floor. Then have a friend measure from the binding to the floor.
Add 1 to 2 inches to the measurement (2 to 3 inches for mountain bikes). This will give you a minimum Stand Over Height.
This Stand Over Height will allow you to stand over your bike while leaving enough clearance above the top tube of the frame.
Enter the final measurement in inches into the Inches box (use the decimal equivalent for fractions Examples: 1/2 = .5 1/4 = .25).
Your minimum Stand Over Height is: Millimeters Write down your calculated minimum Stand Over Height. Then refer to the Size Guide Charts for the bikes you're considering.