One Rep Max Calculator
Estimate the most you can lift once from a lighter set, using four trusted formulas at once.
FitnessScience-backed formula
Enter your details
Fill in the fields, then calculate
Enter the weight.
Enter reps (1-20).
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Enter your details and tap Calculate to see your results appear here.
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ResultYour result appears here.
What One Rep Max Means
Your one-rep max is the heaviest weight you can lift once with good form. It sets the baseline for programming every other set.
Effort and heart rate map neatly onto your training zones.
Testing a true max is risky, so these formulas estimate it from a lighter set you can complete for several reps.
The estimate holds best when reps stay under about ten.
How to Use This Calculator
- Enter the weight you lifted.
- Enter the reps you completed.
- Tap Calculate to see four estimates and a percentage table.
The Formula Used
Epley: weight × (1 + reps / 30)
Brzycki: weight × 36 / (37 − reps)
Brzycki: weight × 36 / (37 − reps)
- weight
- The load you lifted.
- reps
- Clean reps completed.
Understanding Your Results
Strength training
90-100% of 1RM
Low reps, heavy loads.
Hypertrophy
70-85% of 1RM
Moderate loads for muscle growth.
Endurance
50-65% of 1RM
Lighter loads, higher reps.
Estimate caps out
Above 10 reps
Accuracy fades with very high reps.
Tips to Improve
- Test with a weight you can lift 3 to 6 times.
- Use full, controlled reps for honest numbers.
- Re-test every few weeks of training.
- Warm up well before any heavy set.
Frequently Asked Questions
They are close within about ten reps. Beyond that, accuracy drops.
Epley and Brzycki are the most common and agree closely for low reps.
Only with experience, a spotter, and a solid warm-up. Estimates are safer for most lifters.
Scientific References
- Epley, B. (1985). Poundage Chart. Boyd Epley Workout. Lincoln, NE.
- Brzycki, M. (1993). Strength testing: Predicting a one-rep max from reps to fatigue. JOPERD, 64(1), 88–90.
- LeSuer, D. A., et al. (1997). The accuracy of prediction equations for estimating 1-RM. Journal of Strength and Conditioning Research, 11(4), 211–213.