What is your estimated 1RM?
Your estimated 1RM is the heaviest load you could lift once, calculated from a set you actually did instead of measured directly. With the Epley formula, 1RM = weight × (1 + reps / 30): 100 kg for 5 reps estimates 117 kg. It is an estimate, not a measurement, and it loses accuracy as reps climb. Under 10 reps it is dependable; past 12 treat it as a reference rather than a number.
The formula
Epley: 1RM = weight × (1 + reps / 30). Brzycki: 1RM = weight × 36 / (37 − reps). The two agree almost exactly at 10 reps and diverge from there: Epley returns the higher number on long sets, and Brzycki becomes unstable near 37 reps, where its divisor approaches zero.
What each variable means
- Weight lifted
- The load of the set, in whatever unit you use. The formula is unit-agnostic: the result comes out in the same unit that went in.
- Reps completed
- Reps with valid technique. A set taken to failure with a broken last rep inflates the estimate, because the formula assumes every rep counts the same.
Precomputed values
| Reps | Epley | Brzycki | % of 1RM (Epley) |
|---|---|---|---|
| 1 | 103 kg | 100 kg | 97% |
| 3 | 110 kg | 106 kg | 91% |
| 5 | 117 kg | 113 kg | 86% |
| 8 | 127 kg | 124 kg | 79% |
| 10 | 133 kg | 133 kg | 75% |
| 12 | 140 kg | 144 kg | 71% |
| 15 | 150 kg | 164 kg | 67% |
The two formulas cross exactly at 10 reps. Below that Epley reads higher; above it, Brzycki runs away. At 1 rep Brzycki returns the weight lifted, which is the definitionally correct answer, and Epley overshoots by 3%: that is Epley's known limitation near the max. It is why most software uses Epley on long sets and nobody uses either to estimate a single.
Run it on your numbers
How to read the result
Use the estimate to pick the next session's load, not to announce a record. The normal use runs backwards from how it sounds: you estimate the 1RM in order to work at a percentage of it. Training at 80% with an estimated 1RM of 117 kg puts the working load at 94 kg.
Assumptions and limits
- The set was taken close to failure. With reps left in reserve the estimate lands below the real number.
- Accuracy falls as reps rise. Past 12 reps the estimate is indicative only.
- It depends on the lift: in technical movements like the snatch the limit is skill rather than strength, and the formula overestimates.
- It is a statistical estimate across populations, not an individual prediction. Two people with the same set of 5 can have different 1RMs.
