Edge Length Display setting?

Right now when you turn on the Edge Length Display, the Edge Length shows up as a whole number. No decimals. How can I display the decimals like 2.49 Edge Length? When I use Snap to Grid with Edge Length showing, I can’t tell which way it will snap. Say if I want it to snap to 20, and Edge Length is showing to be 19. I can’t tell if it is 19.1 or 19.9. If it is 19.1, it will snap to 19.