One Rep Max Calculator: Based on Scientific Research 

Try it out: powerliftingtechnique.com/one...
You can use it to plan the intensities of your workouts.
For Strength, use 95% of Your 1RM
For Power, use 90% of Your 1RM
For Size, use 80% of Your 1RM
For Endurance, use 70% of Your 1RM