One Rep Max (1RM) Calculator
Your max from a set you already did, and the % table.
The whole load: bar and plates together, or the dumbbell. A 20 kg bar with 40 kg a side is 100 kg.
Clean reps in one set, to the point where one more would have failed or broken form. Estimates are most accurate at 10 or fewer.
Fill in the fields and the answer appears here.
An estimate, not a test. Only try a true one-rep max with solid technique, a proper warm-up and a spotter or coach beside you — and not at all with an injury or a health condition that heavy lifting could worsen.
How this was worked out
Fill in the fields and the answer appears here.
Guide: A set you already did says what you could lift once3 min read
A set you already did says what you could lift once
The heaviest load you can lift for a single rep, the one-rep max, is the most common measure of strength and the base of almost every programme written in percentages. Testing it for real is tiring, demands technique and carries risk. That is what the formulas are for: from a set of several reps taken close to failure, they estimate what you would lift once.
Type in the whole load — bar and plates together — and the clean reps you got. The heavier the set, the better the estimate: three to eight reps is the sweet spot.
Three formulas, side by side
Epley (1985) is the most widely used and is the one shown first. Brzycki (1993) and Lander (1985) sit beside it, with the average of the three. At low reps they almost coincide; above ten they drift apart and all of them lose accuracy, which the page tells you when it happens. Above twenty reps a set measures endurance rather than strength, and the calculator does not estimate from it.
Each was fitted on different lifters and lifts. A well-practised barbell lift reads more reliably than a machine, a dumbbell or a movement you rarely train.
The percentage table
Strength programmes say things like “five sets at 80%”. The table lists 95% down to 50% of the average of the three formulas, with the load and roughly how many reps you could do there. The reps come from Epley turned around and are rounded down: there is no half rep, and erring low is the safe side. The table downloads as a CSV.
When to test for real
For most training decisions the estimate is enough. If you do test a true max, do it with solid technique, a progressive warm-up and a spotter or coach beside you, and never with an injury.
The arithmetic runs in your browser; nothing you type is sent.
How we calculate
Epley (1985)
weight × (1 + reps ÷ 30)
Source: Epley B. Poundage Chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985.
Brzycki (1993)
weight × 36 ÷ (37 − reps)
Source: Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. JOPERD. 1993;64(1):88-90.
Lander (1985)
100 × weight ÷ (101.3 − 2.67123 × reps)
Source: Lander J. Maximum based on reps. National Strength and Conditioning Association Journal. 1985;6(6):60-61.
Frequently asked questions
How do I calculate my one-rep max without testing it?
Take a set you did to the point where one more rep would have failed or broken form, and type in the load and the reps. The calculator estimates the max with three formulas — Epley, Brzycki and Lander — and shows each one and their average, with the arithmetic.
Which 1RM formula is most accurate?
None wins everywhere. Each was fitted on different lifters and lifts, and they agree closely at low reps and drift apart above ten. Epley is the answer shown first because it is the most widely used; the percentage table uses the average of the three, which evens out where each leans.
How many reps should the set have?
Between 3 and 8 gives the most reliable estimate. Above 10 reps the formulas drift apart and the page says so; above 20 a set measures endurance rather than maximal strength, and the calculator does not estimate from it.
What is 80% of my 1RM?
The table under the answer lists 95% down to 50% of the average estimate, with the load and roughly how many reps you could do there — about 7 at 80%. The reps are rounded down: there is no half rep, and erring low is the safe side.
Is it safe to test a real one-rep max?
Only with solid technique, a proper warm-up and a spotter or coach, and not with an injury or a health condition heavy lifting could worsen. For most training decisions the estimate is enough, which is the point of this page.
Does it work in pounds?
Yes. Switch the units to lb; every formula scales with the load, so the arithmetic is the same in either unit.