How to Safely Calculate Your One Rep Max (1RM)

Walk into any commercial gym, and the most common question you'll hear near the bench press is, "What's your max?"

Your One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of an exercise with perfect form. While it's a great metric for tracking strength, physically testing your 1RM is dangerous and incredibly taxing on your central nervous system.

Fortunately, there is a safer way to find your 1RM.

Why Do You Need to Know Your 1RM?

Most popular strength and powerlifting programs (like 5/3/1 or the Texas Method) prescribe workouts based on percentages of your 1RM.

For example, a program might tell you to squat 5 sets of 5 reps at 75% of your 1RM. If you don't know your max, you are just guessing at the weights, which leads to either undertraining or overtraining.

The Formula Method

Sports scientists have developed formulas to accurately estimate your 1RM based on the amount of weight you can lift for higher repetitions. The most famous of these is the Epley Formula.

1RM = Weight Lifted × (1 + 0.0333 × Number of Reps)

If you can bench press 225 lbs for 5 reps, the formula looks like this: 225 × (1 + 0.0333 × 5) = 262 lbs.

Note: These formulas are highly accurate for sets of 2 to 6 reps, but they become wildly inaccurate if you try to estimate a 1RM based on a set of 15 or 20 reps.

Calculate Yours Instantly

Skip the math and use our free 1RM Calculator. Just plug in the weight you lifted and the number of reps you completed, and it will instantly calculate your estimated One Rep Max. It even provides a convenient chart of your training percentages (from 50% up to 95%) so you can program your next workout!