How is one-rep max calculated?
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition. Rather than risk a true max attempt, this calculator estimates it from a lighter set using two well-known formulas:
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
How to use the percentage table
Most strength programs prescribe work as a percentage of your 1RM. For example, hypertrophy work often sits around 67–75% (8–12 reps), while strength work uses 85%+ (1–5 reps). The table above converts your 1RM into exact working weights.
Reps to percentage of 1RM
How heavy a weight you can lift for a given number of reps, as a percentage of your one-rep max — the average of the Epley and Brzycki formulas, exactly as the calculator uses. Multiply any weight by the multiplier to estimate your 1RM. (One rep is, by definition, your 1RM.)
| Reps completed | % of 1RM | 1RM multiplier |
|---|---|---|
| 2 reps | 95.5% | × 1.048 |
| 3 reps | 92.6% | × 1.079 |
| 4 reps | 89.9% | × 1.112 |
| 5 reps | 87.3% | × 1.146 |
| 6 reps | 84.7% | × 1.181 |
| 7 reps | 82.2% | × 1.217 |
| 8 reps | 79.7% | × 1.254 |
| 9 reps | 77.3% | × 1.293 |
| 10 reps | 75% | × 1.333 |
| 11 reps | 72.7% | × 1.376 |
| 12 reps | 70.4% | × 1.42 |
One-rep max chart
Estimated 1RM from the weight you lifted (left) and the reps you managed (top). It works in kg or lb — the units of the answer match the units you lifted in.
| Weight lifted | 2 reps | 3 reps | 4 reps | 5 reps | 6 reps | 8 reps | 10 reps |
|---|---|---|---|---|---|---|---|
| 40 | 41.9 | 43.2 | 44.5 | 45.8 | 47.2 | 50.2 | 53.3 |
| 50 | 52.4 | 54 | 55.6 | 57.3 | 59 | 62.7 | 66.7 |
| 60 | 62.9 | 64.8 | 66.7 | 68.8 | 70.8 | 75.2 | 80 |
| 70 | 73.3 | 75.6 | 77.8 | 80.2 | 82.6 | 87.8 | 93.3 |
| 80 | 83.8 | 86.4 | 89 | 91.7 | 94.5 | 100.3 | 106.7 |
| 90 | 94.3 | 97.1 | 100.1 | 103.1 | 106.3 | 112.9 | 120 |
| 100 | 104.8 | 107.9 | 111.2 | 114.6 | 118.1 | 125.4 | 133.3 |
| 110 | 115.2 | 118.7 | 122.3 | 126 | 129.9 | 137.9 | 146.7 |
| 120 | 125.7 | 129.5 | 133.5 | 137.5 | 141.7 | 150.5 | 160 |
| 140 | 146.7 | 151.1 | 155.7 | 160.4 | 165.3 | 175.6 | 186.7 |
| 160 | 167.6 | 172.7 | 177.9 | 183.3 | 188.9 | 200.6 | 213.3 |
What is my 1RM if I lift 100 kg for 5 reps?
About 114.6 kg — the average of Epley (116.7) and Brzycki (112.5). Five reps sits at roughly 87% of your max.
How do I calculate my 1RM from a 6 rep max?
Multiply your 6-rep weight by 1.181. A 6-rep max of 80 kg gives an estimated 1RM of about 94.5 kg.
What percentage of 1RM is 8 reps?
About 79.7%. Most people can manage around 8 reps at three-quarters to four-fifths of their max, which is why 8–12 reps is the classic muscle-building range.
How often should I retest?
Every 4–8 weeks. Strength changes gradually, so frequent maxing isn't needed and adds fatigue.
Are these estimates exact?
They're close for low-rep sets but individual. Use them as a starting point and adjust based on how the weight actually feels.