Fitness & Performance
One-Rep Max Calculator
Don't test a true max, estimate it. Enter any weight and reps and get your 1RM from four validated formulas.
One-rep max (1RM) is the heaviest weight you can lift once with good form. The Epley formula estimates 1RM as weight × (1 + reps ÷ 30), letting you test strength safely without attempting a maximal lift. Use the result as a training benchmark — retest under the same conditions to track progress.
Epley: W × (1 + reps/30).
Best accuracy below 10 reps.
Percentages of 1RM set training loads.
Calculate Your One-Rep Max (1RM)
Your Estimated 1RM
What Is One-Rep Max (1RM)?
One-rep max (1RM) is the maximum load you can lift once. It anchors percentage-based training: strength at 85%+, hypertrophy at 65–85%, endurance below 65%.
This calculator averages four formulas. Epley, Brzycki, Lombardi, and O'Conner, to give a robust estimate from a submaximal set you can do safely.
How It Is Calculated
Epley: 1RM = W × (1 + reps/30)
Brzycki: 1RM = W × 36 ÷ (37 − reps)
Example: Example: 80 kg × 5 reps → Epley 1RM ≈ 93 kg
Training zones by %1RM
| % of 1RM | Reps | Training effect |
|---|---|---|
| 90–100% | 1–3 | Maximal strength |
| 75–85% | 4–8 | Strength + hypertrophy |
| 65–75% | 8–12 | Hypertrophy |
| < 65% | 12+ | Muscular endurance |
Limitations
- Formula accuracy drops above 10–12 reps.
- Different lifts estimate differently, test each movement.
- True maxes require spotters and technique mastery.
Sources & Review
References used for this calculator’s formulas and thresholds:
One-Rep Max (1RM) FAQ
How do I estimate my 1RM without maxing out?
Lift a weight you can do 3–10 reps with, then apply the Epley formula: W × (1 + reps/30). This keeps you safe while giving a solid estimate.
Which 1RM formula is most accurate?
Epley and Brzycki are the most validated. Averaging all four formulas reduces single-formula error.
How often should I test my 1RM?
Every 8–12 weeks, or let a new rep-max at any weight update the estimate automatically.
Is a 1RM calculator safe for beginners?
Estimating from submaximal sets is safer than testing a true max, but beginners should prioritize technique before heavy loading.
Important disclaimer: Results are educational estimates, not a substitute for professional advice. Review your numbers with a qualified advisor before acting on them.