One Rep Max Calculator

Enter the weight you lifted and how many reps you got to estimate your one rep max, with a percentage chart for programming your next sets.

Unit

Round chart to

Nearest plate load you can actually put on the bar.

Weight lifted

Reps completed

reps

Reps to failure or close to it, with good form.

Estimated one rep max

230.3 lb

Average of five formulas for 200 lb × 5 reps

Epley: w × (1 + r/30): 233.3 lb
Brzycki: w × 36 / (37 − r): 225 lb
Lombardi: w × r^0.10: 234.9 lb
O'Conner: w × (1 + r/40): 225 lb
Wathan: 100w / (48.8 + 53.8e^(−0.075r)): 233.2 lb

Training chart: percentage of your 1RM, rounded to the nearest 2.5 lb, with the reps most lifters can get at that load
% of 1RM	Weight (lb)	Reps
100%	230	1
95%	220	2
90%	207.5	4
85%	195	6
80%	185	8
75%	172.5	10
70%	160	12
65%	150	15
60%	137.5	18–20
55%	127.5	20–24
50%	115	25–30

How this was calculated

Epley: 200 × (1 + 5/30) = 233.3 lb.
Brzycki: 200 × 36 / (37 − 5) = 225 lb.
Lombardi: 200 × 5^0.10 = 234.9 lb.
O'Conner: 200 × (1 + 5/40) = 225 lb.
Wathan: 100 × 200 / (48.8 + 53.8 × e^(−0.075 × 5)) = 233.2 lb.
Average of the five = (233.3 + 225 + 234.9 + 225 + 233.2) / 5 = 230.3 lb.

Estimates are least accurate above 10 reps and for beginners. Never attempt a max without a warm-up, good form and a spotter or safety bars. This is general information, not medical or training advice.

How this one rep max calculator works

Your one rep max (1RM) is the heaviest weight you can lift once with good form. Testing it for real is risky and tiring, so a one rep max calculator estimates it from a lighter set: the weight you lifted and how many reps you managed. The relationship between reps and load is remarkably consistent across lifters, which is why five different researchers fitted five similar formulas to it. Epley says 1RM = weight × (1 + reps ÷ 30); Brzycki says 1RM = weight × 36 ÷ (37 − reps); Lombardi uses weight × reps^0.1; O'Conner uses weight × (1 + reps ÷ 40); and Wathan uses 100 × weight ÷ (48.8 + 53.8 × e^{−0.075 × reps}).

None of them is "the right one". Epley and Wathan run a little high, Brzycki and O'Conner a little low, and they diverge more as the reps go up. This calculator shows all five and reports the average as the headline, which tends to be closer to a measured max than any single formula. A set of one rep needs no formula: that lift is your 1RM, so every method returns the weight unchanged.

Worked example

You bench 200 lb for 5 clean reps. Epley: 200 × (1 + 5/30) = 233.3 lb. Brzycki: 200 × 36 ÷ 32 = 225 lb. Lombardi: 200 × 5^0.1 = 234.9 lb. O'Conner: 200 × 1.125 = 225 lb. Wathan: 20,000 ÷ (48.8 + 53.8 × 0.687) = 233.2 lb. The average is 230.3 lb, so a realistic max attempt would be 225 or 230. The chart under the result then scales that number: 90% is about 207 lb, which rounds to 207.5 lb in 2.5-lb plates, the load at which most lifters can get around 4 reps; 75% is 172.5 lb for a set of 10.

Common mistakes

Using a set that was not near failure. The formulas assume the last rep was close to the last one you could do. If you stopped with three in the tank, the estimate is low.
Plugging in a 20-rep set. Above about 10 reps the formulas drift apart quickly and start measuring endurance rather than strength. The calculator stops at 15; sets of 3 to 6 give the best estimates.
Testing the number instead of training with it. The point of a 1RM estimate is to set working weights (70–85% for most strength programs), not to go for the max the next day.

When the estimate is misleading

The rep-to-load relationship differs by exercise and by person. Lifts with a lot of muscle mass involved, like the squat and deadlift, usually let you do more reps at a given percentage than the bench press or overhead press, so the chart is a guide, not a law. Beginners tend to under-perform on singles because maxing is a skill, and well-trained lifters with a lot of fast-twitch muscle often get fewer reps at 80% than the chart suggests. Machines, bodyweight movements and anything done with a pause or tempo change the numbers too. Use the estimate to program, then let the bar tell you how accurate it was.

Frequently asked questions

›How do you calculate one rep max?

The most common formula is Epley: 1RM = weight × (1 + reps ÷ 30). Lifting 200 lb for 5 reps gives 200 × 1.167 = 233 lb. This calculator averages Epley with Brzycki, Lombardi, O'Conner and Wathan for a steadier estimate.

›How accurate is a one rep max calculator?

Within about 5% for sets of 2–6 reps taken close to failure, and less accurate as reps increase. Above 10 reps the formulas measure endurance more than strength, so the calculator stops at 15.

›What percentage of 1RM should I train at?

Strength work is usually 80–90% for 3–6 reps, hypertrophy 65–80% for 8–12 reps, and endurance under 65% for 15 or more. Most programs set working weights from a 1RM estimate rather than a tested max.

›How many reps can I do at 80% of my max?

Typically about 8. The standard chart runs 95% for 2 reps, 90% for 4, 85% for 6, 80% for 8, 75% for 10 and 70% for 12, though squats and deadlifts usually allow a rep or two more than the bench press.

›Why do the formulas give different numbers?

Each was fitted to a different group of lifters and exercises. Epley and Wathan run slightly high, Brzycki and O'Conner slightly low, and the gap widens with more reps. All five agree exactly at one rep.