What is One Rep Max?
The One Rep Max (1RM) Calculator estimates the maximum weight you can lift for a single repetition based on the weight and number of reps you can perform. This is a fundamental tool for strength training — most training programs are based on percentages of your 1RM.
Testing your actual 1RM can be dangerous, especially for beginners. This calculator safely estimates it from a sub-maximal lift (typically 3-10 reps). The two most popular formulas are Epley and Brzycki, which give very similar results for 1-10 reps.
Strength standards (intermediate male): Bench Press 1RM ~1.0× bodyweight, Squat ~1.5× bodyweight, Deadlift ~2.0× bodyweight. Women typically lift about 60-70% of these numbers relative to bodyweight.
Formula
Epley Formula: 1RM = Weight × (1 + Reps/30) Brzycki Formula: 1RM = Weight × 36 / (37 − Reps)
Training percentages: 100% 1RM = 1 rep (max strength) 90% = 3-4 reps (strength) 80% = 5-8 reps (hypertrophy/strength) 70% = 10-12 reps (hypertrophy) 60% = 15-20 reps (endurance)
Example — 80 kg × 5 reps: Epley: 80 × (1 + 5/30) = 93.3 kg Brzycki: 80 × 36/(37-5) = 90.0 kg Average 1RM ≈ 91.7 kg
How to use this One Rep Max Calculator?
1. Enter the weight you lifted (in kg or lbs). 2. Enter the number of reps you completed with good form. 3. See your estimated 1RM from two formulas and training percentages.
Tip: Use 3-8 reps for the most accurate estimate. Above 10 reps, the formulas become less reliable. Always use a spotter when testing heavy weights.