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One Rep Max

1. Enter the total weight you lifted.
2. Enter the number of reps you performed.
3. Press Calculate.

(It doesn't matter if you're trying to calculate pounds or kilograms. The formula works regardless of which weight type you enter.)

Weight Lifted
Number of Reps
One Rep Max

What is the one rep max?

The maximum amount of weight you can theoretically move for one repetition while maintaining good form.

Why is it important?

There are two primary reasons why people need to find out their one rep max.

  1. Your one rep max can help you determine how much weight you should be lifting to achieve your fitness goals. For example: If you want to build size and strength, you should lift at least 60 percent of your one rep max. If you want to build endurance and tone, you should lift between 30 to 60 percent of your one rep max.
  2. For those of you who simply want to find out how strong you are (or want to compare with your friends), the one rep max can be used as one gauge of a particular muscles' strength.

How do I perform a one rep max test?

  1. Make an appointment with a personal trainer or gym personnel to spot you and make sure you maintain proper form.
  2. Keep your regular routine before the workout. Eat, drink and warm-up the same.
  3. If you are new to working out or haven't trained in a while, let a personal trainer or gym personnel chose a test weight for you to start with.
  4. If you've been training for a while, use the same weight you normally do for the first set.
  5. Do as many reps as you can while maintaining proper form.
  6. If you did more than 10 reps, rest for at least 3 minutes and add more weight, then go back and repeat step 4 again.
  7. Write down the weight and reps.
  8. Repeat these steps for each exercise and/or body part you want to find out your one rep max for. Enter the results in the one rep max calculator and see what yours is.

How is it calculated?

Using this simple formula.

(Weight / (1.0278 - (.0278 * Reps)))

The way to figure it out is by walking through each of the calculations, starting with the innermost brackets. Multiply .0278 by the number of Reps you completed. Then subtract the answer from 1.0278. Finally, take the weight you lifted and divide it by your previous answer. The result is your One Rep Max.

Remember, the one rep max formula is only an estimate, and there are several one rep max formulas available. Your actual one rep max may be higher or lower.

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Updated 11/22/2017