Calculate your One Rep Max for weightlifting.
The One Rep Max (1RM) is the weight you can lift exactly once with proper form. It's the most important metric in strength training for programming, progress tracking, and percentage-based calculations.
1RM = Weight × (1 + Reps / 30)
Example: 175 lbs for 8 repetitions
→ 1RM = 175 × (1 + 8/30)
→ 1RM = 175 × 1.267 = ~222 lbs
Alternative Formulas:
• Brzycki: Weight × 36 / (37 - Reps)
• Lander: 100 × Weight / (101.3 - 2.67 × Reps)
Accuracy decreases above 10 reps
Strength (1-5 Reps): 85-100% of 1RM
Hypertrophy (6-12 Reps): 67-85% of 1RM
Endurance (12-20 Reps): 50-67% of 1RM
Percentage Chart:
• 100% = 1 Rep
• 95% = 2 Reps
• 90% = 4 Reps
• 85% = 6 Reps
• 80% = 8 Reps
• 75% = 10 Reps
• 70% = 12 Reps
For beginners: No! Maximal attempts carry injury risk. Use the calculator with 3-5 clean reps instead. Actual 1RM testing is relevant for powerlifters, not regular training.
Very accurate at 1-6 reps (±5%). Still usable at 7-10 reps (±10%). Above 10 reps, the estimate becomes unreliable as endurance factors in more than maximal strength.
For percentage-based training (e.g., 5x5 @ 80%). Many programs like Starting Strength, 5/3/1, or GZCL use 1RM percentages. It also helps measure progress objectively.
Every 4-8 weeks or when training feels too easy/hard. Some programs (like 5/3/1) have built-in progression. Listen to your body!
Pro Tip: Use a set where you went to technical failure with clean form. "Cheated reps" will skew the result!