One Rep Max Calculator

Category: Sports
- April 07, 2025
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Calculate your one-rep max (1RM) based on the weight you can lift for multiple repetitions. This calculator supports different formula methods for more accurate estimations.

Exercise Information

Weight & Reps

Advanced Options

About One Rep Max (1RM)

One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. Directly testing your 1RM can be risky, which is why these formulas are used to estimate it safely from submaximal lifts.

Common Formulas
  • Brzycki: 1RM = Weight × (36 / (37 - Reps))
  • Epley: 1RM = Weight × (1 + 0.0333 × Reps)
  • Lander: 1RM = (100 × Weight) / (101.3 - 2.67123 × Reps)
  • Lombardi: 1RM = Weight × Reps0.1
  • Mayhew: 1RM = Weight / (0.522 + 0.419 × e(-0.055 × Reps))
  • O'Conner: 1RM = Weight × (1 + 0.025 × Reps)
  • Wathen: 1RM = Weight / (0.488 + 0.538 × e(-0.075 × Reps))
Tips for Accurate Estimation
  1. For best results, use reps in the 1-10 range
  2. Different formulas may be more accurate for different exercises
  3. Formula accuracy tends to decrease as reps increase
  4. Consider using the average of multiple formulas for better estimates
Training Applications
  • Use your 1RM to determine appropriate working weights for different rep ranges
  • Track changes in your 1RM over time to measure strength progress
  • Program strength cycles based on percentages of your 1RM
  • Set realistic strength goals based on your current 1RM

What Is a One Rep Max (1RM) Calculator?

The One Rep Max Calculator is a strength max tool that estimates the maximum amount of weight you can lift for a single repetition—commonly referred to as your 1RM. Instead of attempting a risky max-effort lift, this calculator helps you estimate your 1RM using safer, submaximal lifts and widely accepted formulas.

Common Formulas Used

These formulas are based on established strength training research. Each offers a different way to calculate your one rep max depending on the number of reps and weight lifted.

Brzycki: 1RM = Weight × (36 / (37 - Reps))

Epley: 1RM = Weight × (1 + 0.0333 × Reps)

Lander: 1RM = (100 × Weight) / (101.3 - 2.67123 × Reps)

Lombardi: 1RM = Weight × Reps0.1

Mayhew: 1RM = Weight / (0.522 + 0.419 × e(-0.055 × Reps))

O'Conner: 1RM = Weight × (1 + 0.025 × Reps)

Wathen: 1RM = Weight / (0.488 + 0.538 × e(-0.075 × Reps))

How to Use the Calculator

Follow these simple steps to estimate your 1RM and enhance your training precision:

  • Select the exercise (e.g., Bench Press, Squat, or enter a custom one).
  • Enter the amount of weight lifted and the number of reps you performed.
  • Choose your preferred calculation method or view estimates using all formulas.
  • Click "Calculate 1RM" to get your estimated max lift.
  • Review detailed breakdowns, visual charts, and a percentage table for training insights.

Why Use a One Rep Max Calculator?

This tool is more than a rep max guide—it's a key part of a smarter training strategy. Here's why it's useful:

  • Provides safer 1RM estimates without the need for max-effort lifts.
  • Helps set precise training loads based on percentages of your 1RM.
  • Tracks strength improvements over time.
  • Adapts to your needs with multiple formula choices and unit options.

Training Applications

Your estimated 1RM can support various fitness goals and calculators, such as:

Frequently Asked Questions

Is this calculator safe to use?

Yes, it allows you to estimate your 1RM using lower-risk submaximal lifts, avoiding unnecessary strain or injury.

Which formula should I choose?

If you're unsure, Brzycki is a solid default—especially effective for rep ranges under 10. You can also view all formula results to compare.

Does the unit (kg or lb) matter?

No worries—just select your preferred unit. The calculator adapts accordingly and presents results in your chosen format.

How accurate is the estimate?

Accuracy can vary based on the number of reps and the formula used. For best results, use rep counts between 1 and 10 and consider averaging across multiple formulas.

Final Thoughts

Whether you're fine-tuning your workout plan, setting new lifting goals, or adjusting your calorie maintenance level, this one rep max calculator can be an effective tool in your fitness toolkit. Use it to stay informed, train smart, and get the most from your workouts.