One Rep Max (1RM) Calculator
Your one rep max (1RM) is the heaviest weight you can lift for a single rep. This 1RM calculator estimates it safely from a lighter set, like 80 kg for 6 reps, using the Epley formula plus six others, and builds a percentage chart so you can plan your training weights.
Using validated formulas like Epley (1RM = weight × (1 + reps/30)) or Brzycki, you can safely project your single-rep maximum from submaximal sets of 1 to 10 reps, avoiding the injury risk of testing a true 1RM alone.
Estimated One Rep Max (1RM)
Epley FormulaBased on lifting 100 kg for 5 reps. The average across all 7 scientific formulas is 115.5 kg.
7-Formula Average
115.5 kg
Consensus value
Brzycki Formula
112.5 kg
Alternative estimate
Reps Tested
5 reps
High accuracy range
Training Load & Rep Percentage Chart
| % 1RM | Weight (kg) | Typical Reps |
|---|---|---|
| 100% | 116.7 kg | 1 |
| 95% | 110.9 kg | 2 |
| 90% | 105 kg | 4 |
| 85% | 99.2 kg | 6 |
| 80% | 93.4 kg | 8 |
| 75% | 87.5 kg | 10 |
| 70% | 81.7 kg | 12 |
| 65% | 75.9 kg | 15 |
| 60% | 70 kg | 20 |
| 55% | 64.2 kg | 20+ |
| 50% | 58.4 kg | 25+ |
Hypertrophy training is typically performed between 65% and 85% of 1RM.
All 7 Scientific Formulas Compared
| Formula | Estimated 1RM |
|---|---|
| Epley (Default) | 116.7 kg |
| Brzycki | 112.5 kg |
| Lombardi | 117.5 kg |
| O'Conner | 112.5 kg |
| Mayhew | 119 kg |
| Wathan | 116.6 kg |
| Lander | 113.7 kg |
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Clinical Equations
WHO, CDC, ACSM & Mifflin-St Jeor
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How to use One Rep Max Calculator
- 1Select your preferred units (kg or lb) and enter the weight lifted.
- 2Input the repetitions completed with good form (1 to 12 reps).
- 3Review your consensus 1RM estimate, multi-formula comparison table, and percentage-based training weight chart.
How 1RM estimation formulas work
Testing a true 1RM can cause extreme joint strain and carries high injury risk if done without experienced spotters. Submaximal mathematical models allow lifters to predict peak strength with high precision from sets of 3 to 10 repetitions.
The Epley and Brzycki equations are the gold standards in exercise science. Formulas agree closely between 2 and 6 reps, but begin to diverge past 10–12 reps due to muscle endurance differences.
Percentage-based training zones
90–95% 1RM: Peak strength (1–3 reps); 80–87.5% 1RM: Heavy strength & hypertrophy (4–6 reps); 70–77.5% 1RM: Hypertrophy & volume (8–12 reps); 60–67.5% 1RM: Muscular endurance and explosive speed work (12–15+ reps).
Frequently Asked Questions
Which 1RM formula is most accurate?
Epley and Brzycki are the most consistent for sets under 10 repetitions. Brzycki is widely favored for upper-body pressing (bench press), while Epley performs exceptionally well for squats and deadlifts.
Is it safe to test a true 1RM?
Testing a true 1RM places maximum load on tendons, ligaments, and joints. Estimating your 1RM from submaximal repetitions is substantially safer and accurate enough for programming.
How do I use the percentage chart?
Use 80–85% for strength blocks (3–6 reps), 70–80% for muscle hypertrophy blocks (8–12 reps), and 60–70% for explosive power or technique training.
Can I use this for any exercise?
It is calibrated for major multi-joint compound barbell lifts: bench press, squat, deadlift, and overhead press. It is less reliable for isolation machine exercises.
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Scientific Sources & Evidence
- World Health Organization (WHO) — Body Mass Index Classification
- CDC Growth Charts — BMI-for-age LMS Percentiles
- Mifflin et al. (1990) — Basal Metabolic Rate Predictive Equations
- NICE Guideline NG246 — Identification and Management of Overweight and Obesity
- American College of Sports Medicine (ACSM) — Exercise Testing & Prescription
- European Food Safety Authority (EFSA) — Dietary Reference Values for Water