One rep max calculator
Enter a weight and the number of clean reps you did with it. You get your estimated one-rep max, a percentage chart and the weights to train with for strength, muscle and endurance — without ever attempting a max.
- Epley, Brzycki and Lombardi formulas
- Percentage chart in kg or lb
- Free, no sign-up
Most accurate with 2–10 reps.
116.7kg
Epley formula — the one the AI Workout tracker uses
Percentage chart
Working weights from your estimated max, with roughly how many reps you can do at each.
| % of 1RM | Weight | Reps |
|---|---|---|
| 100% | 117.5 kg | 1 |
| 95% | 110 kg | 2 |
| 90% | 105 kg | 4 |
| 85% | 100 kg | 6 |
| 80% | 92.5 kg | 8 |
| 75% | 87.5 kg | 10 |
| 70% | 82.5 kg | 12 |
| 65% | 75 kg | 15 |
| 60% | 70 kg | 20 |
Rounded to the nearest 2.5 kg.
Training zones
- Strength100–117.5 kg85–100% · 1–5 reps
- Muscle growth77.5–100 kg67–85% · 6–12 reps
- Muscular endurance57.5–77.5 kg50–67% · 12–20 reps
How your one-rep max is estimated
The heavier a weight is, the fewer times you can lift it — and that relationship is predictable enough to work backwards. Strength formulas take a set you did and estimate the single heaviest rep you could manage on the same day.
The main result uses the Epley formula. The Brzycki and Lombardi estimates are shown beside it: all three agree closely between 3 and 6 reps and drift apart as the reps climb, which is why a set of 2–10 reps gives the most trustworthy number.
- Epley: weight × (1 + reps ÷ 30)
- Brzycki: weight × 36 ÷ (37 − reps)
- Lombardi: weight × reps^0.10
Example
80 kg for 8 reps: 80 × (1 + 8 ÷ 30) ≈ 101 kg estimated max.
Three rules for a number you can trust
- 01Use a hard set with clean formThe set should end within a rep or two of failure, with no rep where your technique broke down. Easy sets underestimate your max; sloppy reps overestimate it.
- 02Use a fresh setTake it from early in the workout, not the last set after everything else. Fatigue can knock several kilos off the estimate.
- 03Stick to free-weight compound liftsThe formulas were built on squats, bench presses and deadlifts. On machines and isolation exercises they are much less reliable.
Your max, updated after every set
With AI Workout Pro you don't need a calculator. The workout tracker estimates your one-rep max from every set you log, keeps your personal records for each lift and suggests the weight for every set — so your training keeps pace as you get stronger.
Build my training plan- Estimated 1RM and PRs for every lift
- A suggested weight for each set
- Strength trends charted over time
One rep max questions
What is a one rep max (1RM)?+
Your one rep max is the heaviest weight you can lift for a single repetition with good form. Training programs use it as a reference point: instead of prescribing exact kilos, they prescribe a percentage of your max, so the same program fits a beginner and an experienced lifter.
How accurate is a 1RM calculator?+
With a hard set of 2–10 reps on a compound lift, estimates usually land within a few percent of a tested max. Accuracy drops with higher reps, with sets that ended far from failure, and on machines or isolation exercises. Treat the result as a solid starting point, not an exact number.
Which 1RM formula is the most accurate?+
No single formula wins for everyone. Brzycki tends to be closest at low reps, Epley reads slightly higher at moderate reps, and all of them become less reliable above 10. If the three estimates here are close, you can trust the number; if they spread apart, use a heavier set with fewer reps.
Should beginners test their one rep max?+
There's no need. A true max attempt is when technique is most likely to break down, and in your first months your max changes from week to week anyway. Estimating it from a set of 3–8 reps gives you nearly the same information with far less risk.
How often should I recalculate my 1RM?+
Every 3–4 weeks is plenty, or whenever the weights in your program start to feel clearly too light or too heavy. Compare like with like: the same exercise, in a similar rep range, at a similar point in your workout.
Know your numbers. Now get a plan.
AI Workout turns your goals, equipment and schedule into a complete training plan — and adjusts it every week as you get stronger.