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One Rep Max Calculator

Estimate Your Maximal Strength Safely

Enter the weight you lifted and the number of reps to estimate your 1RM.

Formulas are most accurate between 1-10 reps.

Your Estimated 1RM

Enter your lift details to see your estimated one-rep maximum.

Understanding One Rep Max (1RM)

What is a One Rep Max?

A One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of a specific exercise with proper form. It is considered the "gold standard" for measuring absolute strength in exercises like the bench press, squat, and deadlift.

Knowing your 1RM is essential for structured strength programs, as many routines prescribe intensity as a percentage of your 1RM (e.g., "Perform 3 sets of 5 reps at 80% of your 1RM").

Why Use a Calculator Instead of Testing?

Testing a true 1RM can be extremely taxing on the central nervous system and carries a higher risk of injury, especially for beginners. A 1RM calculator allows you to estimate your maximal strength using submaximal loads (weights you can lift for multiple reps), which is safer and easier to integrate into a regular workout.

The Formulas Explained

Our calculator uses several scientifically validated formulas to give you a well-rounded estimate:

  • Epley Formula: One of the most popular formulas. $1RM = W \times (1 + \frac{R}{30})$. It tends to be very accurate for most lifters.
  • Brzycki Formula: $1RM = W \times \frac{36}{37 - R}$. This formula often provides a slightly more conservative estimate.
  • Lander Formula: $1RM = \frac{100 \times W}{101.3 - 2.67123 \times R}$. Developed by McGlothin in 1993.
  • O'Conner Formula: $1RM = W \times (1 + 0.025 \times R)$. Another simple and effective linear model.

Where $W$ is weight lifted and $R$ is repetitions performed.

How to Improve Your 1RM

  1. Progressive Overload: Gradually increase the weight, frequency, or number of repetitions in your training.
  2. Proper Technique: Efficient movement patterns allow you to move more weight safely.
  3. Specific Strength Phases: Incorporate blocks of training focused on low reps (1-5) and high intensity (85%+).
  4. Recovery: Strength is built during rest. Ensure you are getting enough sleep and nutrition.

Safety Precautions

  • Always use a spotter when testing heavy weights.
  • Warm up thoroughly before attempting any heavy sets.
  • If your form breaks down, the rep doesn't count toward a 1RM estimate.
  • Consult a doctor before starting a high-intensity strength program.

Frequently Asked Questions

They are very accurate when the repetitions are low (between 2 and 10). Once you go above 10-12 reps, the formulas become less reliable because endurance starts to play a larger role than absolute strength.

No. Testing a true 1RM is very stressful. Most athletes only test their 1RM every 8-12 weeks or at the end of a training cycle.

Yes. You will have a different 1RM for every exercise. Your deadlift 1RM will typically be much higher than your overhead press 1RM.

Training Tips

  • Use a spotter for safety.
  • Record your lifts to check form.
  • Rest 3-5 mins between heavy sets.
  • Stay hydrated during workouts.
  • Track progress in a lifting log.

Important Links

All Health Calculators Lean Body Mass Calculator Macro Calculator Calorie Burned Calculator
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Strength Training:

Safety Disclaimer

Heavy lifting involves inherent risks. This calculator provides estimates only. Always prioritize proper form over weight. If you are new to strength training, seek guidance from a certified fitness professional.