One Rep Max Calculator
Safely estimate your maximum strength potential based on your current lifts.
The Epley Formula
Developed by Boyd Epley in 1985, this formula is a standard in strength training for estimating one-rep maxes from sub-maximal efforts.
1RM = Weight × (1 + Reps/30)
WeightAmount of weight lifted
RepsNumber of repetitions performed
Manual Calculation Example
Estimate the 1RM for a lift of **225 lbs** performed for **5 reps** using Epley.
1
Divide Reps
Divide reps by the constant 30.
5 / 30 ≈ 0.1667
2
Add One
Add 1 to the result.
1 + 0.1667 = 1.1667
3
Multiply by Weight
Multiply by the weight lifted.
225 × 1.1667
4
Result
Estimated One Rep Max.
1RM ≈ 262.5 lbs
Training Zones by Percentage
Once you know your 1RM, you can design your training based on specific goals:
- Strength (85-100%): Low reps (1-5), high intensity. Increases pure strength.
- Hypertrophy (70-85%): Moderate reps (6-12). Best for building muscle size.
- Endurance (50-70%): High reps (12-20+). Improves muscular endurance.
Frequently Asked Questions
What is a 1RM?
1RM stands for One Repetition Maximum. It is the maximum amount of weight you can lift for a single rep with proper form.
Why use a calculator instead of testing it?
Testing a true 1RM places immense stress on the body and carries a higher risk of injury. Calculators allow you to estimate it safely from your regular working sets.
Is the calcuation the same for all lifts?
The formulas are general approximations. They tend to be most accurate for upper body compound lifts like the Bench Press, but are widely used for Squats and Deadlifts as well.