One Rep Max Calculator
Enter the weight and reps from a recent hard set. You get an estimated one rep max plus a %1RM table you can plan your training around.
Estimated one rep max
117 kg
Second estimate: 113 kg
The headline uses the Epley formula, the same one Liftoff runs on every logged set. The second estimate uses Brzycki as a cross-check; your true max usually sits between the two.
| % of 1RM | Weight | Typical reps |
|---|---|---|
| 95% | 111.2 kg | ~2 |
| 90% | 105.3 kg | ~4 |
| 85% | 99.5 kg | ~6 |
| 80% | 93.6 kg | ~8 |
| 75% | 87.8 kg | ~10 |
| 70% | 81.9 kg | ~12 |
| 65% | 76.1 kg | ~15 |
| 60% | 70.2 kg | ~18 |
How it works
The main estimate uses the Epley formula, weight × (1 + reps ÷ 30), which is the same math Liftoff runs every time you log a set. We show the Brzycki estimate alongside it as a cross-check; the truth usually sits between the two.
Rep-max formulas are most accurate in the 2-10 rep range. Past that, fatigue styles differ too much between lifters for any formula to stay sharp.
Getting the most out of it
Use a recent, hard set
The estimate is only as good as the set you feed it. Pick one taken close to failure within the last couple of weeks.
Keep reps at 10 or fewer
A tough set of 5 predicts your max far better than a burnout set of 20.
Don't test what you can estimate
Max-out singles are fun but costly to recover from. Estimate weekly, test rarely.
Plan with percentages
Use the %1RM table to set working weights: ~80% for strength work in the 5-8 rep range, ~70% for volume.
FAQ
Your one rep max (1RM) is the heaviest weight you could lift for a single rep of an exercise with sound form. Most programs prescribe working weights as a percentage of it.
Within a few percent when the input set is in the 2-10 rep range and taken close to failure. Accuracy drops as reps climb, because endurance starts to matter more than raw strength.
Rarely, and only if you're experienced and warmed up with a spotter. For programming purposes an estimate is nearly as useful and far cheaper to recover from.
The headline number is the Epley formula, the same one the Liftoff app uses to score your logged sets. Brzycki is shown as a second opinion.
Pick working weights from the percentage table, for example 3×5 at ~85% for strength or 3×10 at ~70% for hypertrophy, and nudge the weight up as the reps get easier.
Liftoff does this math on every set.
Log a set in Liftoff and it estimates your 1RM, updates your charts, and ranks the lift, automatically.
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