1RM Calculator
Estimate your one-rep max (1RM) from the weight lifted and number of reps. 5 recognized formulas and percentage chart.
Your data
Between 1 and 30 reps
Everything about 1RM calculation
Why calculate your 1RM?
The 1RM (one repetition maximum) is the heaviest weight you can lift once with proper form. It's the gold standard in strength training for programming workouts and tracking progress.
Testing your actual 1RM is risky, especially without a spotter. Our calculator estimates it from a weight and rep count using 5 proven formulas: Epley, Brzycki, Lander, Lombardi, and O'Conner.
The percentage chart helps plan your sets: work at 70% of 1RM for hypertrophy, 85% for strength, 90%+ for maximal strength.
Who uses this calculator?
- Weightlifters
- Estimate your max lift without injury risk and program training cycles by percentage.
- Fitness coaches
- Individualize training loads for athletes based on their estimated 1RM for each exercise.
- Powerlifters
- Track squat, bench press, and deadlift progress with reliable estimates between competitions.
- Strength coaches
- Program periodization cycles (strength, hypertrophy, endurance) based on 1RM percentages.
How to estimate your 1RM
Enter the weight lifted (kg or lbs) and the number of reps performed (2-12 for reliable estimates).
The calculator displays your estimated 1RM from all 5 formulas and their average.
Check the percentage chart to find the right weight for your training goal (hypertrophy, strength, endurance).
Frequently asked questions
- What is 1RM in strength training?
- 1RM (One Repetition Maximum) is the maximum weight a person can lift once on a given exercise with proper form. It's the benchmark for measuring strength and programming training.
- Which 1RM formula is most accurate?
- Brzycki's formula is often considered most accurate for 1-10 rep sets. Epley's is the most well-known with similar results. Beyond 10 reps, all formulas lose accuracy. The average of formulas is generally the best estimate.
- How many reps are optimal for estimating 1RM?
- Estimates are most reliable between 2 and 6 reps. Beyond 10 reps, muscular endurance interferes and formulas overestimate 1RM. For precise estimation, use a weight you can lift 3-5 times with good form.
- How to use 1RM percentages?
- 1RM percentages guide programming: 50-65% for muscular endurance (15-20 reps), 67-85% for hypertrophy (6-12 reps), 85-95% for strength (1-5 reps). These are classic benchmarks used in strength and conditioning.
- Is my data saved?
- No. All calculations run in your browser. Your weights and performance are neither transmitted nor stored.
Understanding maximal strength and 1RM
How does the Epley formula for 1RM work?
Epley's formula (1985) is the most widely used: 1RM = Weight × (1 + Reps/30). It establishes a linear relationship between reps and 1RM percentage. For example, lifting 100 kg for 6 reps: 1RM = 100 × (1 + 6/30) = 120 kg. This formula gives reliable results for 1-10 rep sets with about 5% margin of error.
Why are there multiple 1RM formulas?
Different formulas were developed from studies with different populations and methodologies. The relationship between reps and max load isn't strictly linear and varies by individual, exercise type, and training level. That's why no single formula dominates universally.
What is periodization in strength training?
Periodization is the planned organization of training into cycles of varying duration. It uses 1RM percentages to structure phases: accumulation (high volume, 65-75% of 1RM), intensification (heavy loads, 80-90%), realization (peaking, 90-100%), and deload (recovery, 50-60%). This principle optimizes progression while minimizing overtraining risk.