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Your one rep max, or 1RM, is the heaviest weight you could lift for a single good repetition. Testing it directly means loading a bar until it nearly crushes you. A far safer way is to take a set you already did, say 80 kg for 5 reps, and let a formula estimate the rest.
Three formulas, one set
Researchers have fitted many formulas to lifting data. Three are common: Epley, Brzycki and Lombard. For the same set of 80 kg × 5 reps they give slightly different answers.
A spread of about 4 kg on a 90 kg lift. In practice the safest idea is to use the middle or the lower value when you plan heavy work.
How heavy can you go, for how many reps?
Flip the formula around and you get a useful table: the percentage of your 1RM that you can typically lift for a given number of reps. The Brzycki version is easy to remember. Every extra rep costs you around 3 percent at the start and a bit more as the reps climb.
Five reps is about 89 percent of your max, ten reps about 75 percent. Individuals vary, and some people get far more reps at a given percentage than others.
A 1RM turned into training weights
Say your estimated 1RM is 90 kg. Here is what common percentages look like on the bar:
| % of 1RM | Weight | Typical use |
|---|---|---|
| 95% | 85.5 kg | Very heavy singles and doubles |
| 90% | 81 kg | Heavy sets of about 3 |
| 85% | 76.5 kg | Strength sets of about 5 |
| 80% | 72 kg | Solid work sets of about 8 |
| 75% | 67.5 kg | Sets of about 10 |
| 70% | 63 kg | Volume work, sets of 10 to 12 |
| 60% | 54 kg | Warm-ups and technique work |
The 'typical use' column reflects widely used coaching guidelines, not a prescription. Your programme, experience and recovery decide what you actually do.
These ranges overlap and there is no single right answer. Muscle can be built across a wide range if the sets are hard enough.
When the estimate goes wrong
The formulas were fitted to many people, not to you. They also agree best at low and moderate reps. As the number of reps grows, the formulas disagree and fatigue, technique and conditioning matter more than raw strength.
At 12 reps the three formulas differ by nearly 16 kg on a 100 kg set. That is a clear sign to use a heavier, lower-rep set when you want a trustworthy number.
Getting a more reliable number
- Use a heavy, clean set. Aim for 3 to 6 reps with good form and a rep or two still left in the tank.
- Do the same lift each time. A bench press 1RM says nothing about your squat.
- Track it over time. A rising estimate matters more than any single reading.
- Re-test every few weeks. Strength changes faster than you expect, especially early on.
- Be honest about the set. If you stopped at 5 reps with none left, it is a better data point than 5 reps you could have done 8 of.
Questions people ask
How do I calculate my one rep max?
Use a formula on a set you have done. Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki: 1RM = weight × 36 ÷ (37 − reps). For 80 kg × 5 they give about 93 kg and 90 kg.
Which 1RM formula is most accurate?
None is best for everyone. They tend to agree for sets of about 2 to 10 reps and drift apart above that, so use a heavy, low-rep set for the most reliable estimate.
What percent of my 1RM is five reps?
Roughly 89 percent using the Brzycki formula. Ten reps is about 75 percent. Individual differences can be large.
Is it safe to test my true one rep max?
It carries more risk than lighter work. Use a spotter or safety bars, warm up well and stop if form breaks. An estimate from a set of 3 to 6 reps is usually enough.
How often should I recalculate my 1RM?
Every few weeks is common, or after a training block. Beginners often see their estimated max change quickly, so re-test more often.