Try it out here. xRM was created to help lifters assess their potential 1 - 12 rep max. xRM uses the Brzycki formula to calculate maxes.
Enter the weight and the number of reps you can perform with the given weight and hit Go. xRM will calculate and display your rep maxes up to 12 reps. Please keep in mind that the maxes are just estimates. Always use care when working with heavy weights and be sure to listen to your body.