One Rep Max Calculator
Estimate your 1RM from any working set. Enter the weight and reps you performed to instantly calculate your maximum strength and full training percentage table.
Estimated 1RM (Epley — Recommended)
Epley ★
116.7 kg
Brzycki
112.5 kg
Mayhew
119.0 kg
Training Percentages
Based on Epley 1RM estimate of 116.7 kg. Round to nearest 2.5kg plate increment.
1RM Formulas Explained
Brzycki: 1RM = weight / (1.0278 − 0.0278 × reps)
Mayhew: 1RM = (100 × weight) / (52.2 + 41.9 × e^(−0.055 × reps))
Epley (1985) is the most widely used and validated formula. Brzycki is more conservative and tends to be accurate for lower rep ranges. Mayhew was developed from bench press research and works well for upper body lifts.
Frequently Asked Questions
What is a 1 Rep Max (1RM)?
Your 1 Rep Max is the maximum amount of weight you can lift for a single repetition with good form. It's the gold standard for measuring absolute strength in exercises like squat, deadlift, bench press, and overhead press. It's used to set training percentages across all strength and powerlifting programmes.
How many reps should I use to estimate 1RM?
The most accurate predictions come from lower rep ranges (1–5 reps) close to your maximum. As you go above 10 reps, the formulas become less reliable because muscular endurance plays a bigger role. For the best estimate, use a weight where you reach failure between 3–8 reps.
How accurate are 1RM prediction formulas?
For rep ranges of 1–10, most formulas are accurate to within 5–10% of your true 1RM. The Epley formula is the most widely validated and works well across most athletes. Individual variation exists — some athletes are better at higher rep ranges (more endurance-adapted) while others excel at low reps (more neural drive). Track your actual 1RM periodically to calibrate.
Why does 1RM matter for training?
Training intensity in strength programmes is prescribed as a percentage of your 1RM (e.g. '4×4 at 80% 1RM'). Knowing your 1RM lets you train at the exact intensity prescribed, which ensures progressive overload and appropriate stimulus. Without a 1RM, you're guessing at intensity and likely undertrained or overtrained.
How often should I test my 1RM?
For most athletes, testing 1RM every 8–16 weeks is sufficient. More frequent testing can interfere with training if done with true maximal attempts. Instead, use submaximal testing (e.g. an estimated 1RM from 3RM or 5RM efforts) more frequently to track progress without the fatigue of true maximal lifts.
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