One-Rep Max (1RM) Calculator
Estimate your true one-rep max from any sub-maximal set using six published formulas (Epley, Brzycki, Lombardi, Lander, O'Conner, Wathen).
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One-Rep Max (1RM) Calculator
Generated on April 25, 2026
Estimate your one-rep max (1RM) — the heaviest weight you can lift once with proper form — from a sub-maximal set. Useful for building training plans without actually attempting a true 1RM (which is risky and exhausting).
Estimated 1RM (average of 6 formulas)
114.9 kg
Predicted Working Weights
Based on your estimated 1RM of 114.9 kg.
| Reps | % of 1RM | Weight |
|---|---|---|
| 1 | 100% | 114.9 kg |
| 2 | 95% | 109.2 kg |
| 3 | 93% | 106.9 kg |
| 4 | 90% | 103.4 kg |
| 5 | 87% | 100 kg |
| 6 | 85% | 97.7 kg |
| 8 | 80% | 91.9 kg |
| 10 | 75% | 86.2 kg |
| 12 | 70% | 80.4 kg |
| 15 | 65% | 74.7 kg |
Step-by-step calculation
Formula
Epley: 1RM = w × (1 + r/30). Brzycki: 1RM = w × 36/(37 − r). Lombardi: 1RM = w × r^0.10.
- 1You lifted 100 kg for 5 reps.
- 2Epley = 100 × (1 + 5/30) = 116.67 kg
- 3Brzycki = 100 × 36 / (37 − 5) = 112.5 kg
- 4Lombardi = 100 × 5^0.10 = 117.46 kg
- 5Average of 6 published formulas = 114.9 kg
- 6Working-weight table is computed as % × 1RM, where % comes from standard rep-intensity tables.
?What is the One-Rep Max (1RM) Calculator?
The One-Rep Max (1RM) Calculator estimates the heaviest weight you can lift once with proper form, based on a sub-maximal set you've actually performed. Attempting a true 1RM is risky (high injury potential), exhausting, and requires a spotter, so most lifters use prediction formulas instead. This calculator averages six widely-cited formulas — Epley (1985), Brzycki (1993), Lombardi (1989), Lander (1985), O'Conner (1989), and Wathen (1994) — to give a robust estimate, then projects your training weights for any rep range from 1RM down to 15RM. Used by powerlifters, bodybuilders, CrossFit athletes, and rehab clinicians.
The Formula
All six formulas are statistical regressions fit to thousands of real-world lifters. They agree closely for moderate reps (3-8) but diverge at higher rep counts (12+) where individual variability dominates. Brzycki is the most commonly cited; Epley is slightly more accurate for compound movements (squat, deadlift, bench); Lombardi tends to underestimate at low reps. For a balanced estimate use the average — that's what this calculator's headline number gives. None of these formulas work for repetitions beyond 15 (the relationship between reps and intensity becomes too non-linear).
% of 1RM by Reps — Working Weight Reference
Standard relationship between reps and intensity (% of 1RM). Use to plan training sets.
| Reps | % of 1RM | Training adaptation | Example use |
|---|---|---|---|
| 1 | 100% | Maximum strength | Powerlifting meet, true max |
| 2 | 95% | Maximum strength | Heavy doubles |
| 3 | 93% | Strength | Powerlifting / heavy training |
| 5 | 87% | Strength | 5×5 programs (StrongLifts, Starting Strength) |
| 6 | 85% | Strength | 5/3/1 main work |
| 8 | 80% | Strength + hypertrophy | Hypertrophy training |
| 10 | 75% | Hypertrophy | Bodybuilding standard |
| 12 | 70% | Hypertrophy + endurance | Higher-rep bodybuilding |
| 15 | 65% | Muscular endurance | Endurance / metabolic conditioning |
Put It in Perspective
The current raw bench-press world record is 355 kg (Julius Maddox) — heavier than two adult tigers.
An untrained adult male typically benches 0.5-0.8× body weight; intermediate trainees 1.2-1.5×; advanced 1.8-2.0×; elite 2.5×+.
Squat ratios run higher: untrained ~0.75×; intermediate ~1.5×; advanced ~2.25×; elite 3×+.
Practical Examples
Bench-pressed 100 kg for 5 reps → estimated 1RM ~115 kg.
Squatted 140 kg for 3 reps → estimated 1RM ~150 kg.
Deadlifted 180 kg for 8 reps → estimated 1RM ~225 kg (use Brzycki for the most reliable estimate at 8+ reps).
Power-hypertrophy training: work at 70-85% of 1RM (5-12 reps). Maximum strength: 85-95% (1-5 reps). Endurance: 60-70% (12-20 reps).
Powerlifting meet warm-up: bar → 40% → 60% → 75% → 85% → 92% → 96% → 100% (your opener) → 102-105% (your second/third attempts).
Frequently Asked Questions
Popular Conversions
Jump to a ready-made conversion — useful for quick reference and sharing: