1RM Calculator
Estimate your one rep max from any recent hard set — no need to test a true max. Enter the weight, the reps you got, and how hard the set felt (RPE), and get your 1RM plus training percentages.
Calculator
Estimated 1RM: 115.9 kg
Based on 100 kg × 5 reps @ RPE 10.
Training percentages
| % of 1RM | Weight |
|---|---|
| 95% | 110.1 kg |
| 90% | 104.3 kg |
| 85% | 98.5 kg |
| 80% | 92.7 kg |
| 75% | 86.9 kg |
| 70% | 81.1 kg |
| 65% | 75.3 kg |
| 60% | 69.5 kg |
| 55% | 63.7 kg |
| 50% | 57.9 kg |
Estimated rep maxes (RPE 10)
| Reps | Weight |
|---|---|
| 2RM | 110.7 kg |
| 3RM | 106.8 kg |
| 4RM | 103.4 kg |
| 5RM | 100 kg |
| 6RM | 97 kg |
| 8RM | 91.1 kg |
| 10RM | 85.6 kg |
Want to lift one of these weights? Use the plate calculator to see what to load on the bar.
How this 1RM calculator works
Every combination of reps and effort corresponds to a percentage of your one rep max. An all-out set of 5 (RPE 10) sits at about 86.3% of 1RM; a set of 5 with one rep in reserve (RPE 9) sits at about 83.7%. Divide the weight you lifted by that percentage and you get your estimated max. This RPE-based approach, popularised by powerlifting coaches like Mike Tuchscherer, is more accurate than classic formulas such as Epley or Brzycki because it accounts for how hard the set actually was.
RPE to percentage of 1RM
This is the lookup table the calculator uses. Find your reps in the left column and your RPE across the top — the cell is the percentage of your 1RM.
| Reps | RPE 10 | RPE 9.5 | RPE 9 | RPE 8.5 | RPE 8 |
|---|---|---|---|---|---|
| 1 | 100% | 97.8% | 95.5% | 93.9% | 92.9% |
| 2 | 95.5% | 93.9% | 92.2% | 90.7% | 89.2% |
| 3 | 92.2% | 90.7% | 89.2% | 87.8% | 86.3% |
| 4 | 89.2% | 87.8% | 86.3% | 85% | 83.7% |
| 5 | 86.3% | 85% | 83.7% | 82.4% | 81.1% |
| 6 | 83.7% | 82.4% | 81.1% | 79.9% | 78.6% |
| 7 | 81.1% | 79.9% | 78.6% | 77.4% | 76.2% |
| 8 | 78.6% | 77.4% | 76.2% | 75.1% | 73.9% |
| 9 | 76.2% | 75.1% | 73.9% | 72.3% | 70.7% |
| 10 | 73.9% | 72.3% | 70.7% | 69.4% | 68% |
| 11 | 70.7% | 69.4% | 68% | 66.7% | 65.3% |
| 12 | 68% | 66.7% | 65.3% | 64% | 62.6% |
Frequently asked questions
What is a one rep max (1RM)?
Your one rep max is the heaviest weight you can lift for a single repetition of an exercise with proper form. Training programs commonly prescribe working weights as a percentage of your 1RM, so knowing it (or a good estimate) lets you follow almost any strength program.
How is 1RM estimated without maxing out?
Any set taken close to failure predicts your 1RM: the weight you lifted, the reps you got, and how hard it felt (RPE) map to a percentage of your 1RM. For example, 5 reps at RPE 10 (an all-out set) is about 86.3% of your 1RM, so lifting 100 kg for 5 hard reps predicts a 1RM of roughly 115 kg. This is safer than testing a true max and nearly as accurate for sets of 2 to 6 reps.
What is RPE and why does it matter here?
RPE (Rate of Perceived Exertion) measures how hard a set felt on a 6-10 scale. RPE 10 means you could not have done another rep; RPE 9 means one rep was left in the tank; RPE 8 means two. A set of 5 at RPE 8 uses a lower percentage of your 1RM than a set of 5 at RPE 10, so factoring in RPE makes the estimate much more accurate than reps alone.
How accurate are 1RM calculators?
Estimates are most reliable for low-rep, high-effort sets: 2-6 reps at RPE 8-10. Accuracy drops as reps climb, which is why this calculator stops at 12 reps. Individual factors like fatigue, technique, and how well the exercise suits you can shift your true max a few percent in either direction.
Should I train with my full 1RM?
Rarely. Most strength programs prescribe working sets between 65% and 95% of your 1RM depending on the goal: heavier for strength (80-95%), moderate for hypertrophy (65-80%). Use the training percentages table to find your working weights, and consider a Training Max (90% of 1RM) if you run programs like 5/3/1.
Hardy tracks your 1RM automatically
Log your workouts in the Hardy app and it estimates your 1RM from every hard set, suggests working weights from your Training Max or RPE targets, and handles progression for you.
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/r/HardyApp