Trying to figure out if a bike will fit you is a difficult task especially when you can't see it in person! There is also a lot of mis-information online about how to properly size a bicycle. Let us see if we can help you understand what to look for when sizing an electric bike.
Myth - Use the seat height from the ground (#2) to size a bike.
While many people want the ability to stand flat footed, that is actually a very bad thing to do with a bicycle. If you can stand flat footed on a bike when stopped, when you pedal your knees will come up near your chest which may cause knee pain and also make the bike uncomfortable to ride and also difficult to reach the handle bars as you will have to lean back more.
How did this myth come about?
Traditionally bicycles were required to include their 'Standover Height' - #3 in the image above. When a bicycle rider stops you are supposed to stand in front of the seat, by knowing the standover height it will ensure the top bar on the bicycle will not hit you in a delicate area! Now that many electric bikes do not include a top bar, and overseas manufacturers do not comply with US CPSC regulations, customers are now confusing the height of the seat from the ground with the Standover Height.
How should you size a bike?
The first dimension in the image above (pedal to seat) is how you should size a bicycle. It will ensure that you are able to pedal a full circle. The simple equation to determine that distance for a road bike is: 1.09 * Inseam. For electric bikes where the motor generates a significant amount of power, you can probably go a little less.
Example: 31" Inseam * 1.09 = 33" (rounded down)
What if I want to stand flat footed?
Being able to put your foot down when you first start riding a bike will be ok, but after you get comfortable with a bike you will want to raise your seat up a little more so you don't develop knee pain and are able to push harder on the pedals. The other trick you can do is move the seat as far back as possible as this increases the distance to the pedal without making the seat higher off the ground.
Any other suggestions?
If you still want to see how high the seat will be off the ground without having one of our bikes handy, you can always set the seat of a bike you already have to the same dimensions from the ground just to get an idea of how high it will be.