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One Rep Max Calculator

Estimate your 1-Repetition Maximum (1RM) for bench press, squat, or deadlift using Brzycki, Epley, and Lander formulas.

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Understanding Your Result

The calculation generated by this tool provides an evidence-based assessment derived from established physiological and clinical equations. Use this measurement as an educational indicator alongside broader lifestyle variables, including overall dietary quality, resistance training, cardiovascular endurance, and routine medical checkups.

Mathematical Formula & Scientific Methodology

Epley Formula: 1RM = Weight × (1 + Reps / 30). Brzycki Formula: 1RM = Weight × (36 / (37 - Reps)). Both provide accurate estimations when input reps are between 1 and 10.

\text{Epley: } 1RM = W \times \left(1 + \frac{r}{30}\right) \quad | \quad \text{Brzycki: } 1RM = W \times \frac{36}{37 - r}

Step-by-Step Example Calculation

Bench pressing 100 kg for 5 reps: Epley 1RM = 100 × (1 + 5/30) = 100 × 1.1667 = 116.7 kg (257 lbs).

Clinical Limitations & Nuances

Formulas become significantly less accurate when input repetitions exceed 10 reps due to aerobic energy system involvement.

Frequently Asked Questions

Why estimate 1RM instead of testing a true single?

Submaximal estimation reduces the risk of joint, tendon, and muscular injury associated with maximal absolute strain.

How do I use percentage training loads?

Strength programs typically prescribe working sets at percentages of 1RM: 70-80% for hypertrophy (8-12 reps), 80-90% for pure strength (3-6 reps).

Medically Reviewed Content
SM

Dr. Sarah Mitchell, MS, RD

Exercise Physiologist & Clinical Dietitian

Formulas and educational copy on Body Metric Hub are researched and verified by certified clinical nutritionists and exercise physiology specialists.

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Important Medical & Health Notice

The calculations, tools, and health articles on Body Metric Hub are provided strictly for educational and informational purposes. They do not constitute clinical diagnosis, medical advice, or treatment plans. Calculations are mathematical estimations and cannot replace individual medical evaluation by a licensed physician or registered dietitian. If you are experiencing acute medical symptoms, please contact your local emergency services immediately.