Estimate the heaviest weight you could lift once, from a lighter weight you lifted for several reps.
Your one rep max, or 1RM, is the most weight you can lift for a single clean repetition of an exercise. It is different for each lift, such as the bench press, squat or deadlift. Knowing it helps you pick training weights as a share of your best, and lets you track strength over time. Testing a true 1RM is hard on the body and best done with a spotter, so many people estimate it from a lighter set.
The Epley formula multiplies the weight by one plus the reps divided by 30. The Brzycki formula multiplies it by 36 divided by 37 minus the reps. The Lombardi formula multiplies it by the reps raised to the power 0.10. All three agree closely at low reps and drift apart as the reps go up, and Epley and Brzycki give the same answer at 10 reps. Estimates are best when you use a weight you can lift between 2 and 10 times, and the fewer reps you needed, the closer the estimate tends to be.
The first table shows the weight you could expect to lift for each number of reps, as a share of your estimated 1RM. The second table runs the other way: for a given percentage of your 1RM it shows how many reps you can expect. Lighter weights for more reps suit endurance, moderate weights suit muscle growth, and weights near your maximum for 1 to 3 reps suit strength. Use a spotter for heavy sets and stop if your form breaks down.
Lift a weight you can do between 2 and 10 times, then use a formula. With the Epley formula the 1RM is the weight times one plus the reps divided by 30.
None is best for everyone. Epley and Brzycki are the most used, and they match at 10 reps. Lombardi gives slightly higher numbers at low reps. Try more than one to see the range.
The formulas are built from data on sets of fewer than about 10 reps. Beyond that, fatigue and endurance play a larger part and the estimate becomes less reliable.
It is usually within about 10% of a tested max, and closer when you use fewer reps. Beginners and very fast-improving lifters may see bigger gaps.
It depends on the goal. About 70% to 80% for 7 to 12 reps suits muscle growth, around 70% for 10 to 15 reps suits endurance, and 80% to 100% for 1 to 3 reps suits strength.
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