This is a one rep maximum (1RM) calculator. It allows a lifter the ability to obtain a reasonable estimate of their maximum strength without the need to frequently perform dangerous testing near their limits.
To use this tool, you must first do some strength testing. The closer you get to a one rep max during testing presumably provides a more accurate estimation. It is probably best to keep the test values under 10 reps.
Once testing is done, enter the number of reps and the weight used into the appropriate fields below. Select the 1RM formula to use in the calculation and hit the Calculate button.