One Rep Max Calculator - 1RM Calculator with Multiple Formulas

One Rep Max Calculator

Calculate your 1RM and training percentages

Calculate Your One Rep Max

For best accuracy, use 1-10 reps. Over 10 reps becomes less accurate.
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Estimated One Rep Max

Training Percentages

What is One Rep Max (1RM)?

One Rep Max (1RM) is the maximum weight you can lift for a single repetition of a given exercise with proper form. It's a key metric for measuring strength and programming training loads. Rather than testing your 1RM directly (which carries injury risk), you can estimate it using submaximal lifts.

1RM Formulas

This calculator uses the Brzycki formula, one of the most accurate prediction equations:

1RM = Weight / (1.0278 - 0.0278 × Reps)

Other popular formulas include Epley (Weight × (1 + 0.0333 × Reps)) and Lombardi (Weight × Reps^0.10). Brzycki is most accurate for 1-10 rep ranges.

Using Training Percentages

Once you know your 1RM, you can program training using percentages:

  • 50-65%: Speed work, technique practice (12-20 reps)
  • 65-75%: Hypertrophy (muscle growth) (8-12 reps)
  • 75-85%: Strength building (5-8 reps)
  • 85-95%: Max strength (2-5 reps)
  • 95-100%: Peak strength, competition attempts (1-2 reps)

⚠️ Safety First:

Never attempt your true 1RM without: proper warm-up, experienced spotters, perfect form mastery, and adequate training base (6+ months). For beginners, work in the 5-10 rep range and use this calculator to estimate 1RM. Test actual 1RM only if training for powerlifting competition.

How to Improve Your 1RM

  • Progressive Overload: Gradually increase weight or reps each week
  • Compound Movements: Focus on squat, bench, deadlift, overhead press
  • Strength Rep Ranges: Train primarily in 3-6 rep range for strength
  • Proper Form: Quality reps build strength; poor form causes injury
  • Recovery: Adequate rest between heavy sessions (48-72 hours)
  • Nutrition: Calorie surplus and high protein support strength gains

💡 Programming Tip:

For strength building, train with 75-85% of your 1RM for 3-5 sets of 3-6 reps. For hypertrophy, use 65-75% for 3-4 sets of 8-12 reps. Test your 1RM estimate every 4-6 weeks by performing a heavy 3-5 rep set and recalculating.

Frequently Asked Questions

How accurate is the 1RM calculator? +

1RM calculators are accurate within ±5-10% when using 1-10 reps. Accuracy is highest with 3-5 reps. Beyond 10 reps, accuracy decreases significantly. Individual factors like training style, muscle fiber composition, and fatigue resistance affect results. Use estimates as guidelines, not absolute truth.

Should I ever test my true 1RM? +

Only test true 1RM if: you're competing in powerlifting, you have 1+ years training experience, you have reliable spotters, and you've mastered proper form. For general fitness, testing is unnecessary and increases injury risk. Work in 3-5 rep range and use calculator estimates. Your training doesn't require knowing your exact 1RM.

What's a good 1RM for my body weight? +

Strength standards vary by exercise, gender, and experience. For males: Bench (1.25×BW intermediate, 1.5×BW advanced), Squat (1.75×BW intermediate, 2×BW advanced), Deadlift (2×BW intermediate, 2.5×BW advanced). Women: multiply by 0.6-0.7. These are rough guidelines—genetics and training history significantly affect strength potential.

How often should I retest my 1RM? +

Retest (or recalculate) every 4-8 weeks during strength phases. Beginners can retest monthly as they make rapid gains. Advanced lifters may only test every 8-12 weeks. Avoid testing when fatigued, after deload weeks wait 1-2 weeks, and never test during high-volume training phases. Quality training beats frequent testing.