Why do different 1RM formulas give different results?

Each formula was derived from different training populations and statistical methods. Results vary by 2–10% between formulas. Using multiple formulas and taking the average gives a more reliable estimate.

How accurate are 1RM prediction formulas?

Research shows most formulas are accurate within 5–10% for sets of 3–8 reps to failure. Accuracy decreases for very high reps (15+) or when not taken to true muscular failure.

1RM from Multiple Rep Attempts Calculator

Compare five different 1RM formula estimates (Epley, Brzycki, Lander, Lombardi, O'Conner) from a single rep-weight attempt to find the most likely true maximum.

1RM Multi-Attempt

Compare five different 1RM formula estimates (Epley, Brzycki, Lander, Lombardi, O'Conner) from a single rep-weight attempt to find the most likely true maximum.

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Enter values above and press Calculate to see the result.

How It Works

Compare five different 1RM formula estimates (Epley, Brzycki, Lander, Lombardi, O'Conner) from a single rep-weight attempt to find the most likely true maximum

Each component has a specific meaning:

Single rep-weight attempt — The single rep-weight attempt recorded for the scenario being assessed.

Note: Interpret the 1rm multi-attempt result against the thresholds and context described above.

How to Use

Enter the single rep-weight attempt for the scenario you are assessing. Compare five different 1RM formula estimates (Epley, Brzycki, Lander, Lombardi, O'Conner) from a single rep-weight attempt to find the most likely true maximum. Use the 1rm multi-attempt result to inform your calculation.