One Rep Max (1RM) Calculator
Estimate your one-rep max from a set you have already done, without the risk of a true max attempt. See the result from three standard formulas and a chart of working weights by percentage.
Estimated one rep max
| % of 1RM | Weight | Typical reps |
|---|
How to estimate your one rep max
- Enter the weight and the number of clean reps you completed in a hard set.
- Read the estimated 1RM (the average of the three formulas) and each formula's result.
- Use the percentage chart to pick working weights: for example 70–80% for sets of 8–10, or 85% and up for heavy sets of 3–5.
How 1RM formulas work
Lifting your true maximum is fatiguing and carries injury risk, so most lifters estimate it from a submaximal set. The Epley formula (weight × (1 + reps ÷ 30)), the Brzycki formula (weight × 36 ÷ (37 − reps)) and the Lombardi formula (weight × reps^0.10) are the most widely used. They agree closely for sets of 2–10 reps and drift apart at higher reps, which is why sets under 12 reps give the best estimate.
Use a set taken close to failure with good form. A set where you had five more reps in the tank will underestimate your max. Estimates also vary by person and exercise: people built for endurance often do more reps at a given percentage than the chart suggests.
Percentage-based programs use your 1RM to set training loads. A common guide: 90–95% for 1–3 reps, 80–85% for 5–6, 70–75% for 8–12, and 60–65% for higher-rep or technique work. Log your sets in our free workout log to track how your estimated max climbs over time.
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Frequently asked questions
Which 1RM formula is most accurate?
For 2–10 reps, Epley and Brzycki are both well validated and give similar results. Averaging formulas smooths out their differences.
Is it safe to test a true 1RM?
For experienced lifters with a spotter or safety bars, yes. Beginners are usually better off estimating from a set of 3–5.
Why is my estimate different on another site?
Sites use different formulas. Results within a few percent of each other are normal.
Does it work for any exercise?
It works best for compound barbell lifts like squat, bench press and deadlift.