FitDose

One Rep Max (1RM) Calculator

Estimate the most you could lift for a single rep from a set of up to 12 reps, and see the training loads for every rep range. Works in kilograms or pounds. All calculations run in your browser and nothing is stored.

Your data is not stored or sent to the server. All calculations are performed locally in your browser.

Your set
kg

Use a set taken close to failure with good form. Sets of 10 reps or fewer give the best estimate.

Results

Enter the weight you lifted and how many reps you did.

Reps and percentage of 1RM

How many reps are typically possible at each percentage of your one rep max, from the NSCA Training Load Chart.

Reps% of 1RM
1100%
295%
393%
490%
587%
685%
783%
880%
977%
1075%
1270%

How it's calculated

Epley (1985): 1RM = weight × (1 + reps ÷ 30)Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps)Lombardi (1989): 1RM = weight × reps^0.10

Sources: Brzycki, JOPERD 1993; LeSuer et al., J Strength Cond Res 1997; Reynolds et al., J Strength Cond Res 2006; NSCA Training Load Chart

Last reviewed

Frequently asked questions

What is a one rep max?

Your one rep max (1RM) is the heaviest weight you can lift once with good form for a given exercise. Coaches use it to set training loads as a percentage, such as 80% of 1RM.

How is 1RM estimated from reps?

Formulas such as Epley, Brzycki and Lombardi scale up the weight you lifted based on how many reps you completed. They agree closely at low reps and drift apart as reps increase, so this calculator shows all three and their average.

How many reps should I use?

Ten or fewer. Research comparing sets of 5, 10 and 20 reps found the 5-rep set predicted 1RM best, and recommended not using more than 10 reps. A hard set of 3 to 6 reps is a good choice.

Is an estimated 1RM as good as testing it?

It is usually close, and far safer than attempting a true maximum. Accuracy varies by exercise and training experience, so treat the result as a guide and adjust loads based on how sessions feel.

How do I use 1RM to plan training?

Pick a percentage for the rep range you want: around 85 to 95% for heavy sets of 2 to 6, 70 to 80% for sets of 8 to 12. The table shows the loads the NSCA chart pairs with each rep count.

Should I test my 1RM directly?

Only with experience, a proper warm-up and a spotter or safety bars. For most people an estimate from a hard set of a few reps is enough.

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