RunSignUp Results has a flexible system for setting up and automatically calculating divisions. The most common type is Age Groups as shown on the right.
We just added a Quick Age Group Setup capability (the button on right in the screen shot on the right).
You set the lowest age and the highest age and the number of years for each age group, and we will do the auto calculation for you. You can then go in and edit and add age groups. For example you may want a 5 year spread per age group until you get to 70.