Calculate Your One-Rep Max (1RM)
Learn how to compute your one-rep max (1RM) using these calculation methods.
How much ya bench? This number is a rite of passage, and many lifters test it frequently as they progress in the weight room. Perhaps you know that number for the squat as well. But what about the bent-over row? The Romanian deadlift? Or the front squat, cable cross-over, or even the skullcrusher?
You might think your single-rep max (also called one-rep max, One-RM, or 1RM) of those latter moves doesn't matter because you'll never train that heavy on them anyway. But then, one day, you see a program that asks you to use your 65% 1RM on an accessory move or some other unexpected lift.
When that happens, you have to either test for your 1RM or estimate it. Testing it would be a waste of time and poses a risk of injury for certain moves. Fortunately, exercise scientists have already devised a formula that's fairly accurate for most people to determine an estimate for each movement.
Let's say you know you can lift 225 pounds for 10 reps—and only 10 reps, with good form—on the bent-over row. Based on that we can estimate not just your one rep max (100% of your 1RM ), but other loads as well: your 85% 1RM , 70% 1RM , or 55% 1RM , depending on what your program calls for.
Use the calculator below for any lift to estimate your one-rep max based on the amount of weight you can lift on a given move, and the number of clean reps you can achieve before muscle failure. Let's try it for the row, assuming you can do 225 pounds for 10 reps:
One-Rep Max (one-rm) Calculator
Your One-Rep Max (one-rm): ?
95% one-rm 70% one-rm
The calculator estimates your 1RM for the sample rowing exercise to be 300 pounds.
Strength coaches set up programs with percentages based on your 1RM because they don't know your actual strength level, but they know what percentages they want you to be using relative to your single-rep max. The calculator gives you all the relevant loads, which are done simply by multiplying the percentage by your 1RM (in this case, 300 pounds). So if you're doing 85% 1RM , the calculator tells you to use 255 pounds (which is what simply 0.85 x 300).
Some programs are set up a little differently and will instead tell you to do your 3RM, 6RM, or some other number. What's different here is that instead of a giving you a percentage of your one-rep max, you'll see 3RM, which indicates you should use a weight that you can do for three and only three reps. You'll need the table below to essentially do the conversion in a different way.
Let's say your strength workout calls for you to use your 3RM and 5RM for sets of front squats. Say you know you can do 245 pounds for a clean set of 8 reps, but you don't know your one-rep max. If you can just do 8 reps with good form, look at the chart and see that 8 means you're working at 80% of your 1RM (80% 1RM ).
First start by computing your 1RM. That's easy; just divide 245 pounds by 0.80, which estimates your single-rep max to be 306.25, which can be rounded down to 305. To find your 3RM, note that 3 corresponds to 93% ONE-RM, so multiply 305 x 0.93, which estimates your working weight to be 285 (rounded up) pounds. Your 5RM would be 305 x 0.87, giving you a working weight of roughly 265 pounds.
The same program that asked you to do your 3RM and 5RM could have alternately have said to do 93% ONE-RM and 87% ONE-RM, respectively. Those working weights are exactly the same as you can see in the chart below.
1 Rep Max Percentages
Remember that each exercise has its own 1RM. Don't use your back-squat 1RM to compute your front squat, or your underhand-grip bent-over row to determine the reverse-grip version—or any other movement.
Keep in mind also that these are only estimates. The lower your rep count, the more accurate your 1RM estimate will be. Providing the weight you can do for three reps will give you a more accurate number than if you only know what you can do for 10.
JOIN OUR NEWSLETTER!
Be the first to receive exciting news, features, and special offers from Bodybuilding.com!