One-Rep Max

Why do you need to calculate your 1RM?

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.

HOW TO FIND YOUR ONE REP MAX

You might think your single-rep max (also called one-rep max, one-RM, or 1RM) doesn’t matter because you’ll never train that heavy on most lifts anyway. But then, one day, you see a program that asks you to use 65% of your 1RM on a lift.

When that happens, you have to either test for your 1RM or estimate it. Testing your 1RM can be a pretty intense operation, and it requires a high degree of caution to avoid injury. If you do decide you want to test it, watch Layne Norton’s instructions in the video below.

HOW THE 1RM CALCULATOR WORKS: AN EXAMPLE

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.

The calculator estimates 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. Plug that into the calculator above. It’ll show your estimated 1RM to be 300 pounds.

HOW TO USE YOUR 1RM IN A WORKOUT

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). For instance, if you want to do 85% 1RM, the calculator tells you to use 255 pounds (which is 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).

Start by computing your 1RM; 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% 1RM, 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 alternately have said to do 93% 1RM and 87% 1RM, respectively.