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One-rep max calculator
The weight you could lift once, based on the weight and reps of a set. No need to risk testing your max for real.
How it's calculated
The calculator averages two well-known formulas. Epley: weight × (1 + reps / 30). Brzycki: weight × 36 / (37 − reps). At low reps they almost match, at high reps they drift apart, so the average is used.
It's most accurate with sets of 3 to 8 reps. Past 10 reps the error grows, because the set tests endurance more than strength.
Why know your max
Many programs set working weights as a percentage of your max. For example, 75 percent usually gives about 10 reps and 85 percent about 5. The table below the result shows those weights for you.
Safety
A real max is tested only with a warm-up, a spotter and solid form. Regular training doesn't need it: an estimated max is enough to pick your weights.
Frequently asked questions
Which exercises does it work for?
Compound barbell lifts: bench press, squat, deadlift, overhead press. For isolation exercises and machines the estimate is less accurate.
How many reps should I enter?
As many as you managed to failure with good form. If you left two reps in reserve, add them.
How often should I recalculate?
Every 4 to 6 weeks, or when your working weight has clearly gone up. The Tonus app keeps the weights for every exercise in its log.
Sources
- Epley B. Poundage chart. Boyd Epley Workout, 1985
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. JOPERD, 1993 doi.org/10.1080/07303084.1993.10606684
In the app your calorie target updates by itself when your weight changes
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