Why does this calculator show three different 1RM values?

Each equation—Epley, Brzycki, and Lombardi—uses a different regression model derived from distinct datasets and rep ranges. Small differences in the constants and exponents produce slightly different predictions for the same lift, so displaying all three reveals the range of published estimates rather than relying on a single formula.

Which formula is most accurate?

No single formula is universally most accurate across all lifts, rep ranges, and populations. Research comparing these equations typically finds similar accuracy in the 1–10 rep range, with individual variability exceeding differences between formulas. The average provided here is a simple way to synthesize all three.

Can I use this calculator for reps above 10?

The tool accepts up to 20 repetitions, but prediction accuracy declines as reps increase beyond 10. Higher-rep sets are influenced more by muscular endurance and metabolic factors than by maximal strength, making regression-based 1RM estimates less reliable at those rep counts.

Does the average of three formulas improve accuracy?

Averaging three estimates may reduce the impact of any single formula's bias, but there is no peer-reviewed evidence demonstrating that the arithmetic mean of Epley, Brzycki, and Lombardi is more accurate than each formula individually. It is a convenience calculation, not a validated superior method.

What exercises work best with these formulas?

The Epley, Brzycki, and Lombardi equations were developed and validated primarily using compound barbell lifts—squat, bench press, deadlift, and overhead press. Predictions may be less accurate for isolation exercises, machines, or movements with significant technical variability.

Strength Training

Multi-Formula 1RM Comparison Calculator

Compare Epley, Brzycki, and Lombardi 1RM predictions side-by-side from a single lift.

Last updated: 22 April 2026

What this tool does

This calculator estimates one-rep max (1RM) strength by applying three widely used prediction formulas—Epley (1985), Brzycki (1993), and Lombardi (1989)—to a single submaximal lift and displays each result alongside their average. It requires the weight lifted and the number of repetitions completed, then outputs four 1RM estimates in kilograms. These formulas were derived from regression analyses of submaximal-load data and may vary in accuracy depending on rep range, training status, and exercise selection.

Inputs

Result

—

Formula Used

1RM \in {Epley, Brzycki, Lombardi} (w, r)

w

Weight in kg

r

Reps performed

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How Multi-Formula 1RM Comparison Calculator works

This calculator estimates one-rep maximum (1RM) strength using three widely published prediction equations—Epley, Brzycki, and Lombardi—then reports the average of all three alongside each individual estimate. Users enter the weight lifted and the number of repetitions completed, and the tool returns four distinct values: the Epley 1RM, the Brzycki 1RM, the Lombardi 1RM, and the arithmetic mean of the three. Because different formulas prioritize different rep ranges and produce slightly different estimates, comparing all three offers a more complete picture of predicted maximal strength than relying on a single equation.

The formula

The Epley formula is 1RM = weight × (1 + reps / 30). The Brzycki formula is 1RM = weight / (1.0278 − 0.0278 × reps). The Lombardi formula is 1RM = weight × reps^0.10. Each equation takes the same two inputs—the weight lifted (in kilograms) and the number of repetitions—and returns a predicted one-rep maximum. The tool then computes (Epley + Brzycki + Lombardi) / 3 to produce the primary result displayed.

Where this method is most accurate

Prediction equations for 1RM were developed and validated primarily in the 1–10 repetition range, with accuracy declining as repetitions increase beyond 10. The Epley formula is often cited for low-rep sets (1–5), Brzycki for moderate reps (1–10), and Lombardi for similar ranges. All three assume technically proficient repetitions completed without rest-pause techniques, with consistent bar speed, and on compound barbell lifts such as the squat, bench press, and deadlift. Predictions may be less reliable for machine exercises, assistance movements, or individuals with very low or very high training experience.

What this tool does not do

This calculator does not measure actual one-rep-maximum performance, prescribe training loads, diagnose injury risk, or recommend periodization schemes. It does not account for fatigue state, technique breakdown, daily readiness, or individual response variation. The tool produces an estimate from three published equations; it does not tell users how to train, what weight to attempt on a given day, or when to test maximal strength. The average of three formulas is a mathematical convenience, not an evidence-based superior method.

Disclaimer

This tool is for educational and informational purposes only. It is not medical, therapeutic, or professional training advice. The estimates generated are based on population-level regression equations and may not reflect individual performance. Maximal-effort lifting carries inherent risk; users are responsible for their own training decisions, technique, supervision, and safety protocols. Consult qualified coaching and medical professionals before testing or training near maximal loads.

Questions

Why does this calculator show three different 1RM values?: Each equation—Epley, Brzycki, and Lombardi—uses a different regression model derived from distinct datasets and rep ranges. Small differences in the constants and exponents produce slightly different predictions for the same lift, so displaying all three reveals the range of published estimates rather than relying on a single formula.
Which formula is most accurate?: No single formula is universally most accurate across all lifts, rep ranges, and populations. Research comparing these equations typically finds similar accuracy in the 1–10 rep range, with individual variability exceeding differences between formulas. The average provided here is a simple way to synthesize all three.
Can I use this calculator for reps above 10?: The tool accepts up to 20 repetitions, but prediction accuracy declines as reps increase beyond 10. Higher-rep sets are influenced more by muscular endurance and metabolic factors than by maximal strength, making regression-based 1RM estimates less reliable at those rep counts.
Does the average of three formulas improve accuracy?: Averaging three estimates may reduce the impact of any single formula's bias, but there is no peer-reviewed evidence demonstrating that the arithmetic mean of Epley, Brzycki, and Lombardi is more accurate than each formula individually. It is a convenience calculation, not a validated superior method.
What exercises work best with these formulas?: The Epley, Brzycki, and Lombardi equations were developed and validated primarily using compound barbell lifts—squat, bench press, deadlift, and overhead press. Predictions may be less accurate for isolation exercises, machines, or movements with significant technical variability.

Sources & Methodology

Applies the Epley formula (1 + reps/30), Brzycki formula (1 / (1.0278 − 0.0278×reps)), and Lombardi formula (reps^0.10) to the lifted weight, then averages the three results. Epley (1985), Brzycki (1993), and Lombardi (1989) each derived regression models from submaximal-load data.

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