🏋️ One-Rep Max Calculator
Enter any weight and rep count to instantly estimate your 1RM using 7 validated formulas - Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, and Wathan - with an averaged result for best accuracy. The training percentage chart shows your working weights for strength, hypertrophy, and power goals from 50% to 100% of 1RM.
🏋️ 1RM Calculator
Weight Unit
⚠️ Never attempt a true 1RM without an experienced spotter. Estimated 1RMs are most accurate for reps in the 2–6 range. Accuracy decreases above 10 reps.
📊 Training Percentage Chart
Run calculator first. Shows weight to use for every rep range and training goal.
| Reps | % of 1RM | Weight | Zone | Goal |
|---|---|---|---|---|
| Run the calculator first. | ||||
🏆 Strength Standards
Compare your estimated 1RM to population strength standards (bodyweight multiples). Select your exercise above.
📐 1RM Formulas Explained
Epley Formula (Most Common)
Brzycki Formula
Lander Formula
Other Formulas
Training Zones by % of 1RM
❓ Frequently Asked Questions
One Rep Max Calculator - 1RM Estimation, Training Percentages & Strength Standards
Your one rep max is the foundation of percentage-based strength programming. Without it, you're guessing at working weights. With it, you can precisely calculate exactly how heavy to lift for every set in every session - whether you're training for strength, size, or power. This calculator estimates your 1RM from any submaximal effort and then maps out your entire training range from that number.
The 7 1RM Formulas - How They Differ
Seven validated formulas are used in this calculator. They were developed from different research populations and use slightly different mathematical relationships between reps, weight, and estimated 1RM:
Most Widely Used
- Epley (1985): 1RM = w × (1 + r÷30). Most commonly referenced. Good for 2–10 reps.
- Brzycki (1993): 1RM = w × 36÷(37−r). Strong accuracy at 2–10 reps. Gives slightly lower estimates than Epley.
- Lander (1985): 1RM = 100×w÷(101.3 − 2.67123×r). Good balance across rep ranges.
- Lombardi (1989): 1RM = w × r^0.10. Unique power-based formula.
Specialised Formulas
- Mayhew et al. (1992): 1RM = 100×w÷(52.2 + 41.9×e^(−0.055×r)). Developed from bench press research.
- O'Conner et al. (1989): 1RM = w×(1 + 0.025×r). Conservative formula giving lower estimates.
- Wathan (1994): 1RM = 100×w÷(48.8 + 53.8×e^(−0.075×r)). Similar to Mayhew.
- The averaged result across all 7 is the most reliable single estimate.
Training Zones by Goal - How to Use Your 1RM
Once you know your 1RM, use these percentage ranges to set working weights for every training goal:
- Strength (1–5 reps at 80–95% 1RM): Develops maximal force production. Neural adaptations dominate. High CNS demand - needs adequate rest (3–5 minutes between sets). Core of powerlifting programming (5/3/1, Wendler, Texas Method).
- Hypertrophy (6–12 reps at 65–80% 1RM): Maximises muscle growth through metabolic stress and mechanical tension. The "bodybuilding range." Most evidence supports this zone for mass gain. Shorter rest (1–2 minutes) increases metabolic stimulus.
- Power/Olympic lifting (1–3 reps at 50–70% 1RM with maximal speed): Lower load, maximum bar speed. Develops explosive force. Cleans, snatches, jump squats.
- Muscular endurance (15+ reps at 50–65% 1RM): Builds local muscular endurance and cardiovascular capacity. High rep ranges. Sports conditioning and circuit training.
Why Not Just Test Your 1RM Directly?
Direct 1RM testing is used by competitive powerlifters and Olympic weightlifters, but for most gym-goers the risks often outweigh the benefits:
- Injury risk: Maximum attempts demand perfect form at maximum load - any technical breakdown under a true 1RM can cause significant injury. This is particularly true for the spine and shoulders.
- CNS fatigue: True maximal efforts are extremely taxing on the central nervous system. A single 1RM test disrupts training for 2–3 days. Submaximal estimation avoids this cost.
- Accuracy issues: A "true" 1RM on any given day is influenced by sleep, nutrition, warm-up quality, and psychological state. Multiple submaximal estimates averaged over weeks are often more reliable as a training baseline than a single maximum attempt.
When to test directly: when you want a verified competitive number, when you've been training systematically for at least 6 months, and with a spotter present and a thorough warm-up protocol. For programming purposes, an estimated 1RM from a clean 3–5 rep set is entirely sufficient.