Strength Training Formula

One-Rep Max Formula (Epley)

Epley's formula estimates a true 1RM from a submaximal set. It works well at 3–8 reps and starts to drift above 10. For an honest number, use a recent set at 5 reps or fewer.

3 VARIABLESPublished Mar 12, 2026Updated May 10, 2026Live Content

By Orbyd Editorial · AI Fit Hub Team

Best Next MoveStrength

One-Rep Max Calculator

Estimate one-rep max with Epley, Brzycki, and Lombardi formulas.

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Formula 3 variables Worked example Variations

Education · Not medical advice. Output is deterministic math from your inputs.Editorial standards Sponsor disclosure Corrections

Formula

Copy the exact expression or work through it step by step below.

 Epley:    1RM = weight × (1 + reps / 30)
Brzycki:  1RM = weight / (1.0278 − 0.0278·reps)
Lombardi: 1RM = weight × reps^0.10

Variables

1RM

Estimated one-rep max

Predicted maximum load for a single rep with perfect form. Always verify a true 1RM with a controlled max attempt before programming around it.

weight

Submaximal load lifted

Bar weight including plates. Use units consistent across the formula (kg or lb).

reps

Reps completed

Strict reps to technical failure. Drop the last 'half rep' or rep with form breakdown — the equation assumes clean repetitions.

Step By Step

1

Perform a strict set to technical failure at 3–8 reps. Above 10 reps, prediction error grows fast.

Squat 100 kg × 5 strict reps.
2

Plug weight and reps into the equation. Epley is the workhorse default.

100 × (1 + 5/30) = 100 × 1.167 = 116.7 kg.
3

Cross-check with Brzycki and Lombardi when reps are in the 1–3 range. Disagreements over 5 kg suggest the rep count is suspect.

Brzycki: 100 / (1.0278 − 0.0278·5) = 100 / 0.889 = 112.5. Lombardi: 100 × 5^0.10 = 117.5. Range 112–117.
4

Round to the nearest plate increment. Build training percentages off the conservative end of the range when in doubt.

Use 115 kg as the working 1RM. 75% would be 86.25 kg → 87.5 kg in practice.

Worked Example

Squat 100 kg × 5 reps, Epley estimate

Weight (kg)

100

Reps

1RM = 100 × (1 + 5/30) = 100 × 1.1667 = 116.7 kg

Estimated 1RM ~117 kg. Build 80% / 85% / 90% training percentages off this until a fresh max attempt confirms it.

Common Variations

Brzycki: 1RM = w / (1.0278 − 0.0278·r). Most accurate at 1–10 reps.

Lombardi: 1RM = w × r^0.10. Used in some pre-AI Excel calculators.

Mayhew: 1RM = w·100 / (52.2 + 41.9·e^(-0.055·r)). Strong fit for bench press at 7–10 reps.

RPE-based: 1RM = weight / RPE_percent_table[reps][RPE]. Reschedule training around the RPE outcome, not the predicted number.

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Sources & References

Epley B. Poundage Chart — Boyd Epley Workout (1985)
LeSuer DA et al. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift — Journal of Strength and Conditioning Research