One-Rep Max Calculator
Use the calculator above to determine your one-rep max (1RM).

The One-Rep Max (1RM)

A one-rep max (1RM) is the maximum amount of weight you can safely lift one time for a given exercise. Your first workouts in the plan you choose are dedicated to finding your base 1RM. You must do this for each exercise to ensure you start with a reasonable and challenging amount of weight.

A 1RM is a marker of overall strength but is also used as other workout progress indicators. For example, let’s say you begin a new exercise. You test your 1RM and determine that it’s 100 pounds (45.45 kilograms). Thirteen weeks later, you can test your 1RM again in the same exercise. If your 1RM increases, you will be able to objectively say you’ve gotten stronger in that exercise. This is exactly what you’re going to do to measure your increased strength at the end of this program. It's also what you’re going to use to find your starting workout weight.

You can use a 1RM calculator to find your 1RM. A 1RM calculator uses an underlying formula that uses the amount of weight you lifted for a set number of reps. Any online 1RM calculator can provide a good estimate of your 1RM. You can use the calculator above.

Each time you perform a working set, regardless of your number of repetitions, you can calculate a 1RM. So, using the calculator above, you will first find a 12-rep max (12 RM) for each exercise and then use it to determine your base 1RM. Using 12 reps allows you to estimate your 1RM while minimizing your risk of injury. Also, 12 reps minimize the stress on your body during your first workout.

Take caution not to injure yourself when finding your 1RM. Be sure to consult a qualified fitness trainer and ensure that you fully understand how to perform each lift before you start. If you’re not using machines, it’s especially important to use a safety spotter, safety bars, or better yet, both a safety spotter and safety bars.

How to Find Your Base 1RM Using the Above Calculator (with 12 Reps)

Finding your base 1RM has one goal. The goal is to find your starting weight for all your workouts. Do not perform more than 4 working sets per exercise. If you find your 12RM before getting to 4 sets, finish the rest of your sets so that you complete 4 sets with 60% of your calculated 1RM.

  1. Select your starting exercise.
  2. Choose a challenging testing weight, one you think you will be able to lift for 12 repetitions easily, safely and with good form. For example, if you think you can lift 100 pounds (45.45 kilograms) 12 times, use 100 pounds (45.45 kilograms). You don’t want the weight to be too light, but you should also not have to struggle to complete your last rep.
  3. Perform set ONE:
    • Safely attempt to perform 12 repetitions with your testing weight.
      • If you can’t complete at least 8 reps, your weight is too heavy. Go down in weight by 10 pounds (4.45 kilograms), rest for 3 minutes, and try again.
      • If you complete 12 reps, safely and with good form, stop. Enter the weight you used and your 12 reps into the above calculator. It will give you a 1RM calculation.
  4. Perform set TWO:
    • If you feel you can add another 5 pounds (2.27 kilograms) to the weight used during set ONE, add another 5 pounds (2.27 kilograms) to set ONE’s weight. Rest for at least 2 minutes and then perform set TWO using 12 reps. Enter this set into the above calculator. It will calculate another 1RM calculation.
    • If you feel you cannot add another 5 pounds (2.27 kilograms) to the weight used during set ONE, do not add another 5 pounds (2.27 kilograms). Use set ONE’s calculated 1RM as your base 1RM.
  5. Perform set THREE:
    • If you feel you can add another 5 pounds (2.27 kilograms) to the weight used during set TWO, add another 5 pounds (2.27 kilograms) to set TWO’s weight. Rest for at least 2 minutes and then perform set THREE using 12 reps. Enter this set into the above calculator. It will calculate another 1RM calculation.
    • If you feel you cannot add another 5 pounds (2.27 kilograms) to the weight used during set TWO, do not add another 5 pounds (2.27kilograms). Use set TWO’s calculated 1RM as your base 1RM.
  6. Perform set FOUR:
    • If you feel you can add another 5 pounds (2.27 kilograms) to the weight used during set THREE, add another 5 pounds (2.27 kilograms) to set THREE’s weight. Rest for at least 2 minutes and then perform set FOUR using 12 reps. Enter this set into the above calculator. It will calculate another 1RM calculation.
    • If you feel you cannot add another 5 pounds (2.27 kilograms) to the weight used during set THREE, do not add another 5 pounds (2.27 kilograms). Use set THREE’s calculated 1RM as your base 1RM.