1RM Calculator (One Rep Max)
Estimate your one-rep max (1RM) for any lift — bench press, squat, deadlift, overhead press, or any compound movement. Enter the weight you lifted and the number of reps, and this calculator returns your estimated 1RM using the Epley formula, plus your 3RM, 5RM, 8RM, 10RM and 12RM for training programming.
Your one-rep max (1RM) is estimated using the Epley formula: 1RM = weight x (1 + reps / 30). Best accuracy at 3-6 reps to true failure; above 10 reps the estimate drifts high. Example: 100 kg lifted for 5 clean reps gives 1RM = 100 x 1.167 = 116.7 kg. Use the result to set training percentages: 80-87% for strength, 70-80% for hypertrophy, 90-95% for peaking.
When to use this calculator
- You want to know your 1RM without actually testing it (safer + less fatiguing).
- You're programming a training cycle and need your max to compute % loads.
- You're competing in powerlifting and need attempt openers.
- You're tracking strength progress week to week.
- Your coach asks for % of 1RM and you only know "how much you lifted for 5 reps".
Example: 100 kg × 5 reps (back squat)
- Weight: 100 kg.
- Reps: 5.
- Epley formula: 1RM = 100 × (1 + 5 / 30) = 100 × 1.167.
- Estimated 1RM: 116.7 kg.
- Training loads: 3RM ≈ 108.5 kg, 5RM ≈ 101.5 kg, 8RM ≈ 93.3 kg, 10RM ≈ 87.5 kg.
How it works
2 min readThe Epley formula
1RM = weight × (1 + reps / 30)
Developed by Boyd Epley (University of Nebraska strength coach) in 1985, this formula is the most widely used 1RM estimator in strength and conditioning. It's accurate within ±3 – 5 % of your actual 1RM when the submaximal set is performed in the 3 – 6 rep range.
Above 10 reps the estimate becomes unreliable because endurance-type sets depend more on glycolytic capacity than on maximal strength. If you care about a precise 1RM, work up to a heavy triple or single rather than plugging a 12-rep set.
%RM training zones (NSCA)
| %1RM | Reps | Training goal |
|---|---|---|
| 100% | 1 | True max |
| 95–97% | 2–3 | Neural strength |
| 90–93% | 3–5 | Heavy strength |
| 80–87% | 5–8 | Strength + size |
| 70–80% | 8–12 | Hypertrophy |
| 60–70% | 12–15 | Muscular endurance |
| <60% | 15+ | Conditioning / warm-up |
Is Epley the best formula?
It's one of several good options. Others:
For rep ranges of 3–8, all four agree within a couple of percent. Epley is the most popular because the math is easy to do in your head.
When the calculator won't help
Using the result for programming
Related: bench press 1RM estimator, squat 1RM estimator, deadlift 1RM estimator.
Frequently asked questions
How do you calculate 1RM from reps?
Use the Epley formula: 1RM = weight × (1 + reps / 30). Example: 80 kg × 5 reps → 80 × 1.167 = 93.3 kg estimated 1RM. The calculator does this instantly.
How many reps should I use for the most accurate 1RM estimate?
3 to 6 reps. Below 3, the estimate is based on too little data; above 10, endurance becomes a bigger factor than strength and the prediction drifts high.
Is Epley more accurate than Brzycki?
Both are accurate within 3–5% in the 3–8 rep range. Epley tends to slightly over-predict at high reps; Brzycki is slightly more conservative. For practical programming, pick one and stick with it.
Can I use this for bench press, squat and deadlift?
Yes — the Epley formula works on all three big lifts. For more specific estimators see the bench press, squat and deadlift calculators.
Should I actually test my 1RM?
Only in specific contexts: competitions, end of a training block, or occasionally for benchmarking. Weekly 1RM attempts burn your CNS and raise injury risk. Estimating from a heavy triple is safer and about as accurate.
What's the difference between RM, %1RM, and RPE?
RM (rep max) = weight you can lift for exactly N reps. %1RM = percent of your max. RPE (rate of perceived exertion) is 1–10 scale of how hard the set felt. Modern programming uses all three.
Why does the calculator ask for kg or lb?
It doesn't care about units — enter the weight in whatever unit you train with. The output is in the same unit. The formula is dimensionless (just a ratio).
My calculated 1RM seems too high. Why?
Three common reasons: (1) the reps weren't to true failure — you stopped with gas in the tank; (2) the last rep broke form; (3) you used more than 10 reps, where the formula over-predicts. Re-test with a heavier set closer to 3–5 reps at RPE 9–10.