One Rep Max Calculator

Estimate your lifting limits. Computes 1RM capacity using Epley, Brzycki, and Lander models based on submaximal resistance metrics.

Estimates are most accurate for reps under 10.

Calculate Lifting Strength

Enter the weight you lifted and the number of repetitions completed on the left to estimate your one rep max.

Table of Contents

1. What is a One Rep Max (1RM)?

Your **One Rep Max (1RM)** is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. It represents your absolute strength capacity for that movement.

Knowing your 1RM is essential for structuring strength training programs, as training intensities are commonly prescribed as percentages of your 1RM (e.g. performing sets at 80% of 1RM).

2. Mathematical Estimations: Epley vs. Brzycki vs. Lander

Testing your 1RM directly can be physically taxing and carries safety risks. Because of this, sports science researchers have developed formulas to estimate 1RM based on submaximal efforts:

  • Epley Formula: 1RM = Weight × (1 + Reps / 30). Widely used and highly accurate across different repetition ranges.
  • Brzycki Formula: 1RM = Weight / (1.0278 - 0.0278 × Reps). Often preferred for lower repetition ranges (under 10 repetitions).
  • Lander Formula: 1RM = (100 × Weight) / (101.3 - 2.67123 × Reps). An alternative model that yields results similar to the Brzycki equation.

3. Structuring Workouts with Submaximal Percentages

Different lifting intensity zones target specific training adaptations:

  • Maximal Strength (85% - 100% of 1RM): Low reps (1 to 5) that promote neural adaptations and absolute strength. Ensure you consume adequate protein to support muscle recovery. Plan your protein targets using our Protein Calculator.
  • Hypertrophy / Muscle Building (70% - 85% of 1RM): Moderate reps (6 to 12) that support muscle growth. Adjust your macronutrient ratios using our Macro Calculator.
  • Local Muscular Endurance (< 70% of 1RM): High reps (12+) that improve muscular endurance. Check your active calorie burn using our Calories Burned Calculator.

4. Safety Guidelines in Maximal Lift Testing

When testing strength limits, always prioritize safety: warm up thoroughly, maintain proper form, and use a spotter or safety racks. If you are returning from an injury or are new to training, use submaximal estimations rather than testing your 1RM directly.