Formula, in Strength Training

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 variables. Published Mar 12, 2026. Updated May 10, 2026. By AI Fit Hub.

Education, not medical advice. The result comes only from the published formula and your inputs. How we check our formulas.

Formula

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.

Run the numbers next

Strength RPE to Percentage Converter
Convert RPE and reps to percentage of 1RM with a full interactive RPE chart based on the Tuchscherer table.
Strength Progressive Overload Planner
Project lifting progression with weekly overload and planned deload cycles.

Sources

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