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One Rep Max Calculator

Calculate your one rep max (1RM) using proven formulas from your sub-maximal lifts. Get training zones, percentage charts, and safety recommendations for strength training.

The weight you successfully lifted

Number of repetitions completed

Most popular formula - good for 2-10 reps

Accuracy: Very accurate - formulas work best in this range

Quick Tips

• Most accurate with 2-8 reps
• Always use proper form and safety equipment
• Test 1RM only when well-rested and warmed up
• Different exercises may have different 1RM formulas accuracy

How to Use the One Rep Max Calculator

Our 1RM calculator helps you estimate your maximum strength without the risks of testing your actual one rep max:

  1. Choose your unit system (metric kg or imperial lbs)
  2. Enter the weight you successfully lifted for multiple repetitions
  3. Input the number of repetitions you completed with that weight
  4. Select your preferred calculation formula (Epley is recommended)
  5. Click "Calculate 1RM" to get your estimated one rep max

The calculator provides your estimated 1RM, compares all formulas, shows training zones for different goals, and includes a comprehensive percentage chart for programming.

Understanding One Rep Max (1RM)

Your one rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's a fundamental measure of absolute strength and is used extensively in strength training, powerlifting, and athletic performance assessment.

Why Calculate 1RM?

  • Training Programming: Set appropriate loads for different training goals
  • Progress Tracking: Monitor strength gains over time
  • Safety: Avoid the risks of actual 1RM testing
  • Competition Prep: Plan opening attempts for powerlifting meets
  • Periodization: Design effective training cycles

Benefits of Estimation vs Testing

  • Reduced Injury Risk: Lower chance of injury from maximal loads
  • Less Fatigue: Sub-maximal testing causes less CNS stress
  • Frequent Assessment: Can be done more regularly
  • Better Recovery: Faster return to normal training

1RM Calculation Formulas

Our calculator includes eight different validated formulas, each with specific strengths:

Epley Formula (Recommended)

1RM = Weight × (1 + Reps ÷ 30)

Most widely used and validated formula. Works best with 2-10 repetitions and is the standard in many training programs.

Brzycki Formula

1RM = Weight × 36 ÷ (37 - Reps)

Very accurate for 2-10 reps. Often used in research and shows excellent correlation with actual 1RM testing.

Other Formulas

  • Lombardi: Simple formula using reps^0.10 multiplier
  • McGlothin/Lander: Modified version good for higher reps
  • Adams: Conservative estimate, tends toward lower values
  • Baechle: Similar to Epley with different coefficient
  • O'Conner: Conservative formula, good for beginners

Training Zones and Percentages

Once you know your 1RM, you can establish training zones for different goals:

Power Training (85-95% 1RM)

  • Rep Range: 1-3 repetitions
  • Goal: Maximum power and neural adaptations
  • Rest: 3-5 minutes between sets
  • Applications: Powerlifting, Olympic lifting, sports performance

Strength Training (75-85% 1RM)

  • Rep Range: 4-6 repetitions
  • Goal: Maximum strength development
  • Rest: 2-4 minutes between sets
  • Applications: General strength, powerlifting base phases

Hypertrophy Training (65-75% 1RM)

  • Rep Range: 8-12 repetitions
  • Goal: Muscle size and moderate strength gains
  • Rest: 1-3 minutes between sets
  • Applications: Bodybuilding, general fitness, muscle building

Muscular Endurance (50-65% 1RM)

  • Rep Range: 15+ repetitions
  • Goal: Muscular endurance and conditioning
  • Rest: 30-90 seconds between sets
  • Applications: Endurance sports, conditioning, rehabilitation

Accuracy and Limitations

Most Accurate Rep Ranges

  • 2-5 reps: Very accurate (±2-3%)
  • 6-10 reps: Good accuracy (±3-5%)
  • 11-15 reps: Moderate accuracy (±5-8%)
  • 16+ reps: Lower accuracy (±8-12%)

Factors Affecting Accuracy

  • Training Experience: More experienced lifters have more predictable results
  • Exercise Type: Compound movements are more predictable than isolation
  • Muscle Fiber Type: Fast-twitch dominant individuals may exceed estimates
  • Training Status: Fatigue and recovery affect performance
  • Form Consistency: Technique variations can affect results

Frequently Asked Questions

How often should I test my 1RM?

For actual 1RM testing, no more than once every 4-6 weeks to allow proper recovery. Estimated 1RM calculations can be done more frequently, even weekly, to track progress without the stress of maximal loads.

Which formula is most accurate?

Epley and Brzycki formulas are generally most accurate for the 2-10 rep range and are most widely validated. Different formulas may work better for different individuals, so comparing multiple formulas can provide a good range estimate.

Can I use this for any exercise?

These formulas work best for compound movements like squat, bench press, deadlift, and overhead press. They're less accurate for isolation exercises or movements where technique significantly limits performance.

Should I attempt my calculated 1RM?

Only attempt your calculated 1RM if you're experienced, properly warmed up, have a spotter, and are in a safe environment. The calculation is meant to guide training loads, not necessarily to be attempted immediately.

Safety Tips & Best Practices

  • Always warm up thoroughly before testing sub-maximal loads
  • Use proper form - don't sacrifice technique for higher numbers
  • Have a qualified spotter when testing heavy weights
  • Test when well-rested, not after intense training sessions
  • Use conservative estimates for programming initially
  • Track multiple rep ranges to validate your estimates
  • Consider individual factors like training experience and fiber type
  • Don't test true 1RMs frequently - use estimates for regular programming