Understanding Your 1RM & Estimated Reps

Your One-Repetition Maximum (1RM) is the maximum amount of weight you can theoretically lift for a single repetition of a given exercise with proper form. This calculator helps you estimate this value and then derive useful numbers for your training program.

• Tracking Strength Progress: Monitoring how your 1RM changes over time is a key indicator of strength gains.
• Understanding Intensity: The "Estimated Reps" table helps you gauge how many repetitions you might be able to perform at different percentages of your maximum, aiding in set and rep scheme planning.

Actually performing a true 1RM can be physically demanding. This calculator uses established formulas to estimate your 1RM based on a weight you lifted for multiple repetitions.

How to Use This Calculator

1. Select Units: Choose kilograms (kg) or pounds (lbs). This unit will apply to all weight inputs and outputs.
2. Weight Lifted: Enter the weight you successfully lifted.
3. Repetitions Performed: Enter the number of full, successful repetitions you completed with that weight (typically 1-12 for best 1RM estimates).
4. 1RM Formula: Select a formula for the 1RM estimation. Epley is a common choice.
5. Click "Calculate".

Interpreting Your Results

• Estimated 1RM: Your calculated one-rep max.
• Estimated Reps Table: Shows different percentages of your 1RM, the corresponding weight, and an *estimate* of how many reps you might be able to perform at that intensity. This is useful for choosing weights for sets of a target rep range (e.g., finding a weight for sets of 5 reps). The rep estimation in this table primarily uses a reversed Epley formula for consistency.

Common 1RM Formulas Used

This calculator may use one of several common formulas for the initial 1RM estimation:

• Epley Formula: 1RM = Weight * (1 + (Reps / 30))
• Brzycki Formula: 1RM = Weight / (1.0278 - (0.0278 * Reps))
• Lombardi Formula: 1RM = Weight * Reps^0.10
• O'Conner et al. Formula: 1RM = Weight * (1 + (0.025 * Reps))
• Wathan Formula: 1RM = (100 * Weight) / (48.8 + (53.8 * e^(-0.075 * Reps)))

Note on Accuracy: These formulas provide estimates. Actual 1RM and rep capabilities can be influenced by individual factors. The "Estimated Reps" table is also an approximation and can vary.

Tips for Using 1RM Estimates

• Use a weight that you can lift with good form for the chosen number of reps.
• Estimates are generally more accurate when based on lifts performed for 10 reps or fewer.
• Periodically re-test or re-calculate your 1RM as you get stronger.