One Rep Max Calculator
Estimate your maximum lifting capacity without the risk of testing your actual one-rep max.
Training Tip
Understanding One Rep Max (1RM)
One Rep Max (1RM) is the maximum amount of weight that you can lift for a single repetition of a given exercise with proper form. It's a key metric in strength training that serves as a benchmark for your current strength level and helps determine appropriate training loads for different goals.
While directly testing your 1RM by attempting to lift the heaviest weight possible for one repetition is the most accurate method, it carries a higher risk of injury and requires proper preparation and technique. That's why many lifters and coaches prefer to estimate 1RM using mathematical formulas based on the weight you can lift for multiple repetitions.
The Science Behind 1RM Prediction
Several researchers have developed formulas to predict 1RM based on submaximal lifting performance. These formulas are based on the relationship between the number of repetitions performed and the percentage of 1RM that the weight represents.
| Formula | Equation | Best For | Notes |
|---|---|---|---|
| Brzycki (1993) | 1RM = Weight × (36 / (37 - Reps)) | 1-10 reps | Widely used in research; tends to be conservative |
| Epley (1985) | 1RM = Weight × (1 + (0.0333 × Reps)) | 1-10 reps | Simple formula; may overestimate at higher rep ranges |
| Lombardi (1989) | 1RM = Weight × (Reps^0.1) | 4-10 reps | Less commonly used but simple calculation |
| Mayhew et al. (1992) | 1RM = (100 × Weight) / (52.2 + (41.9 × e^(-0.055 × Reps))) | 1-15 reps | More complex but can be more accurate for some exercises |
Note: All formulas become less accurate as the number of repetitions increases beyond 10.
How to Use 1RM in Your Training
Once you know your 1RM (either tested or estimated), you can use it to determine appropriate training loads for different goals:
Strength Development
Intensity: 85-100% of 1RM
Reps per set: 1-5
Rest between sets: 3-5 minutes
Example: If your 1RM for bench press is 100kg, you would use 85-100kg for strength training.
Hypertrophy (Muscle Growth)
Intensity: 67-85% of 1RM
Reps per set: 6-12
Rest between sets: 1-3 minutes
Example: If your 1RM for bench press is 100kg, you would use 67-85kg for hypertrophy training.
Muscular Endurance
Intensity: 50-67% of 1RM
Reps per set: 12-20+
Rest between sets: 30-90 seconds
Example: If your 1RM for bench press is 100kg, you would use 50-67kg for endurance training.
Tips for Accurate 1RM Estimation
- Use a weight that allows 3-8 repetitions: This rep range provides the most accurate estimates across most formulas.
- Perform the set to technical failure: You should be unable to complete another rep with proper form.
- Use proper form: Poor technique can lead to inaccurate estimates and increases injury risk.
- Be well-rested: Fatigue can significantly impact your performance and lead to underestimation.
- Warm up adequately: A proper warm-up ensures your muscles and nervous system are ready for maximal effort.
- Consider exercise specificity: Some formulas work better for certain exercises than others.
- Re-test periodically: Your 1RM will change as you progress, so update your estimates every 4-8 weeks.
When to Test Your Actual 1RM
While estimation formulas are convenient and safer, there are times when directly testing your 1RM might be appropriate:
- Competition preparation: If you're training for a powerlifting or weightlifting competition, practicing with maximal loads is essential.
- After completing a strength cycle: Testing can help evaluate the effectiveness of your training program.
- When you have experienced spotters: Safety should always be the priority when attempting maximal lifts.
- If you're an intermediate or advanced lifter: Beginners should generally avoid maximal testing until they've developed proper technique.
Safety Note: If you decide to test your actual 1RM, always use proper safety equipment (power rack, safety bars, spotters), warm up thoroughly, and maintain strict form. Never sacrifice technique for a heavier weight.