One Rep Max Calculator
Estimate your one-rep max (1RM) from a set you can already do. Enter the weight and reps, and get your 1RM from the Epley and Brzycki formulas plus a full table of training percentages and rep targets — in kg or lb.
Understanding the One Rep Max Calculator
A one-rep max (1RM) calculator estimates the heaviest weight you could lift for a single repetition, without you ever having to attempt a true max. You enter the weight and reps from a set you already completed, and the tool works backward to predict your ceiling. This is safer than testing a real 1RM, which carries injury risk and needs a spotter. Lifters use the estimate to set training loads, track strength progress over time, and program working sets as a percentage of max. It works for any barbell, dumbbell, or machine lift in kilograms or pounds.
How it works
Enter the weight you lifted and the number of reps you completed in a single hard set. The calculator applies two established equations — Epley and Brzycki — and averages them so one outlier formula does not skew the result. From that average 1RM it then builds two tables: an estimated-reps table (the load you could expect to handle for 1, 2, 3, 5, 8, 10, and 12 reps, derived by inverting the Epley equation) and a training-percentage table from 95% down to 65%. Accuracy is highest when the set entered is under about ten reps, because higher-rep sets are influenced too much by conditioning, pacing, and technique.
Worked example
Suppose you bench press 100 kg for 5 reps. Epley gives 100 × (1 + 5/30) = 116.7 kg, and Brzycki gives 100 × 36 / (37 − 5) = 112.5 kg. Averaged, your estimated 1RM is about 114.6 kg. From there, 80% of max is roughly 92 kg for working sets, and the rep table suggests you could handle about 105 kg for 3 reps or 96 kg for 8 reps.
Tips & common mistakes
- Keep the set under about 10 reps — fewer reps give a far more reliable estimate than high-rep sets.
- Use a genuine near-failure set; an easy submaximal set will lowball your true max.
- Re-test with a fresh set every few weeks to track strength changes rather than trusting one old number.
- Treat the percentage table as a starting point and adjust loads to how the bar actually feels that day.
- Always warm up thoroughly and use a spotter or safety pins before attempting heavy singles.
- Different lifts produce different estimates — calculate squat, bench, and deadlift maxes separately.
Sources & methodology
- • Epley, B. (1985). Poundage Chart. Boyd Epley Workout, University of Nebraska.
- • Brzycki, M. (1993). Strength testing: predicting a one-rep max from reps to fatigue. JOPERD.
Related tools
Reviewed by the TopOpenTools editorial team · Last updated June 2026. These tools provide general estimates for educational purposes only and are not financial, tax, insurance, investment, or medical advice. Verify important decisions with a qualified professional.
How to Use This Calculator
- 1Pick kg or lb to match the plates you use.
- 2Enter the weight lifted and reps from a recent hard set, then click Calculate 1RM. Keep it under ~10 reps for the best estimate.
- 3Read your estimated max, then use the percentage table to plan working sets — and check your daily fuel with the TDEE calculator.
Frequently Asked Questions
How accurate is a 1RM estimate?
Estimates are most reliable when the set you enter is under about 10 reps. The fewer reps performed, the closer the formula gets to your true max. Beyond 10–12 reps fatigue and technique vary too much, so the number becomes a rough guide rather than a dependable target.
Which formulas are used?
This calculator uses two of the most established equations — Epley (weight × (1 + reps/30)) and Brzycki (weight × 36 / (37 − reps)) — and shows the average of the two so a single outlier formula does not skew your estimate.
Can it show training weights?
Yes. Once your estimated 1RM is calculated, a percentage table lists common training loads (95% down to 65%) plus the weight you could expect to lift for 1, 2, 3, 5, 8, 10, and 12 reps, so you can plan working sets without testing a true max.