Categories🏋️ Fitness & SportsOne Rep Max (1RM) Calculator

One Rep Max (1RM) Calculator

Estimate maximum weight for 1 repetition using Brzycki & Epley formulas.

Estimated One-Rep Max (1RM)
114.583 kg
Brzycki: 112.5 kg
Epley: 116.667 kg
Training Weight Recommendations
95%
108.854
90%
103.125
85%
97.396
80%
91.667
75%
85.938
Guide & Educational Reference
How to Use the One Rep Max (1RM) Calculator
  1. 1Enter the Weight Lifted during your set.
  2. 2Enter the Repetitions performed (1 to 10 reps recommended).
  3. 3Select weight unit (kg or lb).
  4. 4View your estimated 1RM calculated using Brzycki and Epley equations, plus percentage training weight recommendations.
Understanding One Rep Max (1RM)

One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. Estimating 1RM from submaximal multi-rep sets allows strength athletes to program training percentages safely without testing true single-rep maximums.

Brzycki and Epley 1RM Equations
1. Brzycki Formula

Widely used submaximal 1RM estimation formula for 1 to 10 repetitions.

1RM = Weight × [ 36 / (37 - Reps) ]
2. Epley Formula

Linear 1RM formula developed by Boyd Epley.

1RM = Weight × [ 1 + (Reps / 30) ]
Practical Real-World Example
100 kg Bench Press for 5 Repetitions
Brzycki: 100 × (36 / 32) = 112.5 kg | Epley: 100 × (1 + 5/30) = 116.7 kg
→ Estimated 1RM Average ≈ 114.6 kg (90% training weight = 103 kg)
100 kg for 5 reps
Epley = 100 × (1 + 5/30) = 116.67; Brzycki = 100 × 36/(37−5) = 112.5; Average = (116.67 + 112.5) / 2
→ ≈ 114.6 kg estimated 1RM
225 lb for 3 reps
Epley = 225 × (1 + 3/30) = 247.5; Brzycki = 225 × 36/34 ≈ 238.2; Average ≈ 242.9
→ ≈ 242.9 lb estimated 1RM
Key Tips & Safety Guidance
  • Best Accuracy (1–10 Reps): 1RM formulas are most accurate when input reps are between 1 and 10. Accuracy decreases sharply above 10 reps.
  • Safety First: Estimating 1RM reduces injury risk compared to testing true maximal single lifts.
  • Always use proper lifting form and spotters when training near maximal strength loads.
Frequently Asked Questions

What is a 1RM calculator?

A 1RM calculator estimates the maximum weight you can lift once based on the weight and reps completed in a submaximal set.

Which formula is more accurate, Brzycki or Epley?

Both formulas yield similar results for 1–10 reps. THE CALC displays both formulas and calculates their average.

Which formulas are averaged?

The Epley formula, weight × (1 + reps/30), and the Brzycki formula, weight × 36 / (37 − reps). The calculator reports each and their average.

Why is there a rep limit?

Both formulas lose accuracy at high repetitions, so the calculator only accepts 1 to 30 reps. At exactly 1 rep, the 1RM equals the weight lifted.

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