1RM calculator

Calculate your 1RM (one-rep max) from the weight and reps you did, using the Epley and Brzycki formulas, and get a percentage chart for training.

What 1RM means

Your 1RM (one-repetition maximum) is the heaviest weight you can lift once with good form on an exercise. It is a reference for planning: many strength programs prescribe loads as a percentage of 1RM, for example "4 sets of 6 at 80%".

Testing a true 1RM is demanding and risky if you lack experience or a spotter. That is why it is common to estimate it from a set of several reps taken close to failure.

How it is calculated

This calculator averages two widely used formulas:

• Epley: 1RM = weight × (1 + reps / 30)
• Brzycki: 1RM = weight × 36 / (37 − reps)

Both give similar results between 2 and 10 reps. Beyond 12 reps the estimate loses accuracy, so the calculation is limited to that range.

How to use the result

1. Do a set with a weight that allows 3 to 8 reps with good form, finishing close to failure.
2. Enter the weight and reps.
3. Use the percentage chart to choose your working weight for your goal:
   • Strength: 80–90% of 1RM, 2 to 6 reps.
   • Hypertrophy: 65–80%, 6 to 12 reps.
   • Muscular endurance: under 65%, 15 reps or more.

Limitations

The estimate varies with the exercise, your experience and your muscle fiber makeup: some people can do more reps than others at the same percentage. Treat the number as a guide and adjust based on how your sets feel. Recalculate every 4 to 8 weeks to track your progress.

If you have an injury, pain or a medical condition, check with a professional before doing this exercise.