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Ask A Celebrity Trainer: How Do You Calculate One Rep Max?

Heather Marr is an NYC-based personal trainer and The Model Trainer Method creator, whose A-list client roster includes some of the world’s most famous supermodels. Ahead, she answers a frequently asked question: What is one rep max?

The one repetition maximum – aka one rep max – is your ultimate test of strength. It's the maximum amount of weight you're able to perform for one repetition of the chosen exercise. Obviously, some athletes test themselves for vanity and bragging rights. Others however, test themselves to learn their stats to apply in their programming. Many programs are set up where the gym-goer lifts a percentage of their 1rm for a set number of reps. If you were instructed to lift 75% of your 1rm for x amount of reps, you would simply multiply your 1rm weight by .75 and that would give you the weight to use for your set. 

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How to Calculate One Rep Max 

Other programs are laid out where you will see a number in front of rm. For example, it may read 5rm. This means that you would perform 5 reps of the exercise using the maximum amount you're able to lift. You would not be physically able to do a sixth rep.

1 Rep Max Percentages

1 rep = 100%

2 reps = 95%

3 reps = 93%

4 reps = 90%

5 reps = 87%

6 reps = 85%

7 reps = 83%

8 reps = 80%

9 reps = 77%

10 reps = 75%

11 reps =73%

12 reps =70%

So, using the example of the 5rm above, we would multiply the 1rm by .87 to determine the resistance to use for our set.

Ask a Celebrity Trainer: How Do You Calculate One Rep Max?

To find out your 1rm on an exercise you can get in the gym and physically test yourself on the exercise. This option is best left for experienced lifters or those working with and being supervised by a coach or trainer. Safety comes first. There's no point finding out your 1rm if you're going to get injured in the process, leaving the data totally useless anyway. If you're new in the gym and just starting out, there are lots of formulas you can use to give you an estimate of your 1rm. This is a safe and easy way to give you the information you need for your programs.

Epley (below) is a simple formula that's been around over 30 years and is often used to calculate 1rm.

RM=W*(1+ r/30)

RM= one rep max

W= weight lifted

r= number of reps

Here, a set of 10 reps is a smart choice. If I'm testing my front squat, and I am able to squat 100 lbs. for those 10 reps, I would just plug those numbers into the formula to find out my 1rm.

RM= 100*(1+10/30)


It's important to note that your loads will vary between exercises. For instance, you would not use your front squat data for your bench press 1rm. You would need to calculate that separately. 

Now that you know your 1rm, you’re ready to take your lifting and maybe your boasting to the next level. Following programs, crushing your goals and tracking your progress will be straightforward and uncomplicated. Happy lifting!