One-rep max calculator (1RM)

Your one-rep max (1RM) is the heaviest weight you can lift once with good form. You don't have to test it to know it: lift a weight you can manage for 3 to 8 reps, take the set close to failure, and a formula estimates your 1RM from the weight and rep count. For sets of up to about 10 reps these estimates are usually close enough to plan training with.

How is 1RM calculated?

This calculator runs three of the most widely used prediction equations and shows their average as the main number:

If you enter a single rep, there's nothing to estimate: that weight is your 1RM.

A worked example

Say you bench 60 kg for 8 reps.

• Epley: 60 × (1 + 8 ÷ 30) = 60 × 1.267 = 76.0 kg
• Brzycki: 60 × 36 ÷ 29 = 74.5 kg
• Lombardi: 60 × 8^0.10 = 60 × 1.231 = 73.9 kg
• Average: about 74.8 kg

The three agree within about 2 kg at 8 reps. At 2 to 5 reps they're almost identical. As reps climb they drift apart, which is the spread figure in the result.

How accurate are 1RM calculators?

Reasonably accurate at low reps, less so at high reps. A study of untrained college students by LeSuer and colleagues (1997) compared seven equations against tested maxes on the bench press, squat and deadlift and found high correlations (r above 0.95) for all of them. Reynolds, Gordon and Robergs (2006) tested 5, 10 and 20-rep sets and found the 5RM gave the best prediction, with accuracy dropping as reps went up.

The practical rules:

• 3 to 6 reps is the sweet spot. Heavy enough to reflect max strength, light enough to be safe without a full max attempt.
• Above about 10 reps, endurance starts to matter as much as strength, and two people with the same 1RM can get very different rep counts. That's why this calculator stops at 12 and warns you past 10.
• Reps must be honest. Stopping 3 reps short of failure makes the estimate low. Bouncing the bar or half reps make it high.

What is the %1RM chart for?

Most strength programmes prescribe weights as a percentage of your 1RM, like "4 sets of 6 at 80%". The table under the calculator converts your estimated max into those loads, rounded to the nearest 2.5 kg (or 5 lb) so you can load the bar with standard plates.

The reps column comes from the NSCA training load chart, which pairs each percentage with the number of reps most trained people can do at it:

These are averages, and individuals vary. One study found the number of reps at a given percentage differs between endurance-trained and strength-trained athletes, and it varies between exercises too, so treat the reps column as a starting point. For a fuller walk-through of the percentages and how programmes use them, see the one-rep max percentage chart guide.

How to use your 1RM in training

• Strength: most work at 80 to 90% for sets of 2 to 6.
• Muscle growth: 65 to 80% for sets of 6 to 12 is the classic range, but a 2017 meta-analysis by Schoenfeld and colleagues found muscle growth was similar with light and heavy loads, while heavy loads gave bigger gains in maximal strength.
• Technique and warm-ups: 50 to 60%. A typical warm-up before heavy work is a few sets climbing from 50% up to your working weight.
• Re-estimate every 4 to 8 weeks from a good working set. If you're progressing, your numbers should go up.

You don't need to test a true max to train well. Most lifters, especially beginners, are better off estimating from a set of 5 than grinding out a max single that risks form breaking down. The beginner gym workout plan shows how to progress the main lifts week to week.

Strength relative to bodyweight

Enter your bodyweight and the result shows your lift as a multiple of it, such as a 1.0× bench (bodyweight on the bar). It's a fairer way to compare progress between people of different sizes, and round numbers like a bodyweight bench press make satisfying personal goals. Compare yourself with your own number from two months ago, not with someone else's.

If you're trying to get stronger while losing fat, your lift relative to bodyweight can improve even when the weight on the bar doesn't. Keep protein high (work out your number with the protein calculator) and keep the deficit modest, using the calorie calculator.

Safety notes

• Always use a spotter or safety bars for heavy bench and squat sets.
• Don't attempt a real 1RM in your first few months of training. An estimate from a set of 5 is safer and almost as useful.
• If you have high blood pressure, heart problems, a recent injury or are pregnant, check with a doctor before heavy lifting.

This calculator is for general information and isn't medical advice.