One Rep Max Calculator

How to Calculate Your One Rep Max

Your one rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise. Knowing your 1RM is essential for programming effective training -- most strength and hypertrophy programs prescribe weights as a percentage of your 1RM.

Rather than attempting a true 1RM (which carries injury risk), you can estimate it from a submaximal set. Simply enter the weight you lifted and the number of reps you completed, and this calculator will estimate your 1RM using seven well-established formulas.

The Formulas

This calculator uses seven peer-reviewed formulas to estimate your 1RM:

• Epley (1985) -- The most widely used formula. Works well for 1-10 reps.
• Brzycki (1993) -- Very accurate for low rep ranges (1-7 reps). Popular in academic research.
• Wathan (1994) -- Exponential model often considered the most accurate overall.
• Lander (1985) -- Good accuracy across moderate rep ranges.
• Lombardi (1989) -- Power-based formula. Tends toward conservative estimates.
• Mayhew et al. (1992) -- Exponential model that handles higher rep ranges (8-15) well.
• O'Conner et al. (1989) -- Simple linear model. Conservative but reliable.

We display the average across all seven formulas as your primary estimate. For the most accurate result, use a weight you can lift for 3-8 reps. Accuracy decreases above 10 reps.

Strength Standards

Enter your bodyweight and sex to see how your estimated 1RM compares to population-level strength standards. These standards are based on publicly available data from competitive powerlifting and gym populations, categorized into five levels:

• Beginner -- Less than 6 months of training. Stronger than roughly 5% of lifters.
• Novice -- 6-12 months of consistent training. Stronger than roughly 20% of lifters.
• Intermediate -- 1-3 years of dedicated training. Stronger than roughly 50% of lifters.
• Advanced -- 3-5+ years of serious training. Competitive at a local level.
• Elite -- 5+ years of dedicated training. Competitive at regional or national level.

Tips for Accurate Results

• Use a weight you can lift with good form for 3-8 reps.
• Take the set close to failure (1-2 reps in reserve) for the best accuracy.
• Accuracy decreases significantly above 10 reps.
• Results are estimates -- your actual 1RM may vary based on technique, fatigue, and other factors.
• Never attempt a true 1RM without a spotter and proper warmup.