1RM Calculator
Estimate your one-rep max (1RM) for bench press, squat, deadlift, overhead press, and other lifts from your working sets.
What is a 1RM?
Your 1RM (one-repetition maximum) is the maximum amount of weight you can lift for exactly one clean rep with good form. It is one of the most useful numbers in strength training because it helps you choose appropriate loads for different goals, including strength, hypertrophy, power, and technique practice.
Instead of testing a true max every week, many lifters estimate it from a submaximal set (for example, 225 lb x 5 reps). That is exactly what this calculator does.
How the calculator estimates your one-rep max
Different coaches and researchers use different equations. None is perfect for every person or every lift, so this page includes several models and an average option.
Included 1RM formulas
- Epley: 1RM = weight × (1 + reps / 30)
- Brzycki: 1RM = weight × 36 / (37 − reps)
- Lombardi: 1RM = weight × reps0.10
- O'Conner: 1RM = weight × (1 + 0.025 × reps)
- Mayhew: 1RM = 100 × weight / (52.2 + 41.9 × e−0.055 × reps)
- Wathan: 1RM = 100 × weight / (48.8 + 53.8 × e−0.075 × reps)
How to use this 1RM calculator effectively
1) Use a quality set
Enter a set performed with controlled form and a full range of motion. A grinder with poor technique gives noisy estimates.
2) Stay in a practical rep range
Most equations are best between about 1 and 10 reps. They can still work at higher reps, but accuracy usually drops as fatigue and endurance become bigger factors.
3) Pick the right formula for your context
If you are unsure, use Average. It smooths out formula-specific bias. If you have historical data and one formula matches your real tested maxes best, choose that one consistently.
Training percentages based on your estimated 1RM
Once you know your estimated max, you can quickly assign loads:
- 90–95%: Heavy singles/doubles, max-strength emphasis
- 80–89%: Strength work, low to moderate reps
- 70–79%: Hybrid strength/hypertrophy zone
- 60–69%: Technique volume, speed work, and skill practice
Many athletes also use a training max (commonly 90% of estimated 1RM) to stay conservative and build progress over time.
Limitations and safety notes
- Estimated 1RM is an approximation, not a guarantee.
- Lift type matters: deadlift, squat, and bench can behave differently per individual.
- Sleep, stress, warm-up quality, and nutrition can shift daily strength by several percent.
- Never chase numbers at the cost of technique. Good form is non-negotiable.
Bottom line
A 1RM calculator is a fast way to get a useful strength benchmark without frequent max-out attempts. Use your estimate to plan loads, monitor progress, and adjust training intelligently over time.