Estimate your one-rep max (1RM) using the Epley Formula.
Welcome to the One-Rep Max Calculator! This tool estimates your one-rep max (1RM)—the maximum weight you can lift for one repetition—using the Epley Formula. Input the weight you lifted and the number of reps you performed to get your estimated 1RM in both pounds and kilograms. A chart will also show percentages of your 1RM (e.g., 50%, 70%, 90%), which can help you plan your training program.
Your one-rep max (1RM) is the maximum amount of weight you can lift for one full repetition of an exercise with proper form. It’s a key metric in strength training, helping you gauge your progress and set appropriate weights for your workouts. Testing your 1RM directly can be intense, so this calculator estimates it safely using the weight and reps you can comfortably lift.
We use the Epley Formula to estimate your 1RM:
- 1RM = weight × (1 + (reps / 30))
The result is shown in both pounds and kilograms (1 kg = 2.20462 lbs). The chart displays weights at 50%, 60%, 70%, 80%, 90%, and 100% of your 1RM, which are common percentages used in training programs for different goals (e.g., endurance, hypertrophy, strength).
The calculator converts your inputs as needed:
- Weight: 1 lb = 0.453592 kg, 1 kg = 2.20462 lbs
Your 1RM can guide your training:
- Endurance (50-60%): Use lighter weights for higher reps to build stamina.
- Hypertrophy (70-80%): Moderate weights for 8-12 reps to promote muscle growth.
- Strength (80-90%): Heavier weights for fewer reps to increase raw power.
- Max Effort (90-100%): Use sparingly to test or push your limits, ensuring proper form and safety.
The Epley Formula is an estimate and may not be perfectly accurate for everyone, especially at higher rep counts (above 10) or for certain exercises. Factors like fatigue, technique, and individual physiology can affect the result. For precise measurements, consider working with a coach or testing your 1RM with proper supervision.
Testing your 1RM directly can be risky, especially if you’re not experienced or don’t have a spotter. The calculator provides a safe estimate based on submaximal effort, reducing the risk of injury.
The Epley Formula is one of several methods (others include Brzycki or Lombardi formulas). It’s widely used because it’s simple and effective for most people, but it may be less accurate for very high reps or certain exercises.
Recalculate your 1RM every 4-6 weeks to track progress, especially if you’re following a structured training program. Avoid testing too frequently to prevent overtraining.
Built by xAI, this One-Rep Max Calculator uses the Epley Formula to estimate your 1RM, with support for multiple units and a visual chart. For personalized training advice, consult a fitness professional.