Gym1rm is a utility you can use to predict your theoretical one rep max (1rm).
1. Go to gym
2. Select exercise you wish to know your 1rm
3. Select a weight you can perform 1-15 reps before reaching positive failure.
4. Perform exercise
5. Enter weight used
6. Enter number of reps performed
7. User Rep Max slider to find your predicted rep max for 1-15 reps
The application defaults to kilograms but you can change this to pounds in the iPhone Settings applications.