RM Calculator

1RM Calculator: One Rep Max Strength Calculator

What is One Rep Max (1RM)?

One Rep Max (1RM) is the maximum weight you can lift for a single repetition of an exercise with proper form. It's the gold standard for measuring absolute strength and a cornerstone of strength training programming. Knowing your 1RM helps design effective workout programs, track progress, and set appropriate training loads for different goals (strength, hypertrophy, endurance).

1RM Calculation Formulas

Multiple validated formulas estimate 1RM from submaximal lifts:

• Epley Formula

  1RM = weight × (1 + 0.0333 × reps). Most popular formula, accurate for 1-10 reps. Best for bench press and similar movements.

• Brzycki Formula

  1RM = weight × (36 / (37 - reps)). Conservative estimate, good for beginners. Accurate for 2-10 reps.

• Lombardi Formula

  1RM = weight × reps^0.1. Used in research settings. Works well across different rep ranges.

Why Calculate Your 1RM?

1RM serves multiple important functions in strength training:

• Program Design: Calculate training loads as percentages of 1RM (e.g., 5x5 at 80% 1RM for strength)
• Progress Tracking: Objectively measure strength gains over weeks and months
• Competition Preparation: Plan attempt selection for powerlifting, weightlifting, or strength sport competitions
• Plateau Breaking: Adjust training intensities scientifically when progress stalls
• Goal Setting: Set realistic short-term and long-term strength targets based on current maximums

How to Use the 1RM Calculator

Calculate your 1RM safely without maximal testing:

• Choose Exercise: Select the lift (squat, bench press, deadlift, overhead press, etc.)
• Enter Weight & Reps: Input the weight lifted and number of reps completed with good form (ideally 3-10 reps)
• Select Formula: Choose Epley (most common), Brzycki (conservative), or Lombardi (research-based)
• View Results: See estimated 1RM plus training percentages (60%, 70%, 80%, 90% 1RM) for program planning

Safety and Accuracy Tips

• Test with 3-5 Reps for Accuracy

  Formulas are most accurate when using 3-5 rep sets. Sets above 10 reps become less reliable for 1RM estimation.

• Use Proper Form

  Only count reps performed with correct technique. Cheating reps will overestimate your true 1RM and lead to injury.

• Warm Up Properly

  Before testing, perform progressive warm-up sets: empty bar × 10, 50% × 5, 70% × 3, 85% × 1, then test weight.

• Retest Regularly

  Retest 1RM every 4-8 weeks to track progress and adjust training loads. Strength improves with consistent training.