Estimate your one-rep max (1RM) from a set you’ve already done, without the risk of testing a true max. You’ll also get the weights to use at different percentages of your 1RM for strength or muscle training.
Loading the tool…
How it’s calculated
The calculator averages two widely used formulas:
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
Both are most accurate with heavier sets of 2 to 10 reps. Above about 12 reps the estimates drift a long way from reality.
Worked example
Bench pressing 80 kg for 5 reps gives an Epley estimate of 93.3 kg and a Brzycki estimate of 90 kg, an average of 91.7 kg. For a strength block at 85% of 1RM, that means sets of about 78 kg for around 6 reps.
Using percentages in training
| Goal | % of 1RM | Reps per set |
|---|---|---|
| Maximal strength | 85–95% | 1–5 |
| Muscle growth | 65–85% | 6–12 |
| Muscular endurance | Under 65% | 12+ |
Stay safe
If you do test a true max, warm up thoroughly, use a spotter or safety bars, and stop if your technique breaks down. Beginners usually make faster, safer progress without max testing at all.
Frequently asked questions
What is a one-rep max?
The heaviest weight you can lift once with good form for a given exercise.
How accurate are 1RM calculators?
Usually within a few percent for sets of 2 to 10 reps. They’re less accurate for very high reps or for people new to lifting.
Which formula is best?
Epley and Brzycki give similar results at low reps. Averaging them smooths out the differences.
Does it work for all lifts?
It works best for compound lifts like squat, bench press and deadlift.
Last updated: