One Rep Max (1RM) Calculator
Calculate your one-rep max accurately using proven formulas like Epley and Brzycki. Essential for strength programming.
Knowing your One-Rep Max (1RM) is crucial for structured strength training. Many programs (like 5/3/1 or Smolov) require you to lift a specific percentage of your 1RM.
However, testing your true 1RM frequently is dangerous and highly taxing on your central nervous system. Instead, you can use formulas to estimate your 1RM based on how much weight you can lift for higher reps.
1RM Calculator
Estimated One Rep Max:
Epley Formula:
Brzycki Formula:
*Calculations are estimates. Accuracy decreases significantly for rep counts higher than 10.
How is 1RM Calculated?
There are several mathematical formulas used by coaches and athletes. The two most common are:
1. The Epley Formula (1985)
Formulated by Boyd Epley, the founder of the NSCA.
1RM = Weight × (1 + (Reps / 30))
Source: Epley, B. (1985). Poundage chart.
2. The Brzycki Formula (1993)
Formulated by Matt Brzycki, this is generally considered more accurate for rep ranges under 10.
1RM = Weight × (36 / (37 - Reps))
Source: Brzycki, M. (1993). Strength testing—Predicting a one-rep max from reps-to-fatigue.
Caution: These are estimates. Your actual 1RM depends on neurological adaptations, leverage, and fiber type distribution. Do not attempt a true 1RM without a spotter.
(Want to track your working weight easily? Try Beau, the voice-first workout tracker that logs your sets instantly so you can stay focused. Learn more here.)