One Rep Max Calculator
Estimate your 1RM for any lift.
One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of an exercise with proper form. It's considered the gold standard measure of maximal strength and is widely used in strength training to:
- Track strength progress over time
- Design training programs with appropriate intensity
- Compare strength across different lifters (using relative strength ratios)
- Set goals for competition or personal achievement
Rather than testing a true 1RM (which carries injury risk and requires significant recovery), most lifters use submaximal testing—lifting a lighter weight for multiple reps and calculating their estimated 1RM using validated formulas.
Epley Formula
1RM = Weight × (1 + Reps / 30)
The most widely used formula, developed by Boyd Epley. Simple and accurate for most rep ranges.
Brzycki Formula
1RM = Weight × (36 / (37 - Reps))
Matt Brzycki's formula is particularly accurate for lower rep ranges (1-10). At higher reps, it tends to overestimate.
Which Formula to Use?
For most purposes, the average of multiple formulas provides the best estimate. If you must choose one, use Epley for general training or Brzycki for lower rep testing (5 reps or fewer).
For the most accurate estimate, follow these guidelines:
- Warm up properly - Do 2-3 warm-up sets with progressively heavier weights
- Choose an appropriate weight - Select a weight you can lift for 3-10 reps with good form
- Rest adequately - Take 3-5 minutes before your test set
- Perform the reps - Do as many clean reps as possible, stopping before form breaks down
- Use strict form - No bouncing, excessive body movement, or shortened range of motion
Testing with 3-5 reps gives the most accurate estimate. Higher rep tests (8+) become less reliable due to fatigue, technique breakdown, and mental factors.
Once you know your 1RM, you can program your training using percentages:
Strength Training (85-95%)
1-5 reps per set. Develops maximal strength and neuromuscular efficiency. Best for powerlifters and athletes.
Hypertrophy (65-85%)
6-12 reps per set. Optimal for muscle growth. The sweet spot for most bodybuilders and general fitness.
Muscular Endurance (50-65%)
15+ reps per set. Improves endurance and metabolic conditioning. Good for beginners and conditioning phases.
Frequently Asked Questions
One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's a standard measure of strength used by athletes and trainers to gauge progress and design training programs.
Testing a true 1RM is extremely taxing on your nervous system, increases injury risk, and requires proper spotters and equipment. Using submaximal testing (lifting a weight for multiple reps) is safer and nearly as accurate for training purposes.
Use between 3-10 reps for the most accurate estimates. Lower rep tests (3-5) are generally more accurate. Tests above 10 reps become increasingly inaccurate as fatigue and technique breakdown affect the results.
The Epley and Brzycki formulas are most widely used and validated. Epley tends to work well across rep ranges, while Brzycki is particularly accurate for lower rep ranges (1-10). The average of multiple formulas often gives the best estimate.
Recalculate every 4-8 weeks or at the start of a new training program. Your 1RM changes as you get stronger, so regular updates help ensure your training percentages remain accurate.
These formulas work best for compound barbell lifts like squat, bench press, and deadlift. They may be less accurate for isolation exercises, machine exercises, or movements with significant technique components.
Safety Notice
These estimates are based on mathematical formulas and may not reflect your actual maximum. Never attempt a true 1RM without proper warm-up, spotters, and safety equipment. If you're new to strength training, work with a qualified coach to develop proper technique before testing maximal strength.