One-Rep Max Calculator: How to Calculate Your One-Rep Max

Short for “one-repetition maximum,” one-rep max is a strength standard used by weightlifters, bodybuilders, and powerlifters to determine the maximum amount of weight they can lift in a single repetition for a given exercise. One-rep maximum is often further abbreviated to 1-rep max or 1RM.

The one-rep max is a helpful metric for anyone practicing a strength-training or weight-training program who desires to track their hypertrophy progress (muscle gain). A one-rep max is typically determined by loading a barbell with the heaviest weight you can comfortably lift, performing a deadlift, bench press, or squat for a number of repetitions, then using a fitness calculator to determine your maximum strength level.

There are many one-rep max calculators available online; however, some weightlifters prefer to do the math themselves. In that case, there are several formulas used by 1RM calculators, each one named after the individual credited with formulating it. Simply plug in the weight you lifted in a given exercise (in kilograms) and the number of reps you managed to complete to arrive at an estimate for your one-rep max weight.

1. 1. Brzycki formula: Weight × (36 / (37 – number of reps))
2. 2. Epley formula: Weight × (1 + (0.0333 × number of reps))
3. 3. Lombardi formula: Weight × (number of reps ^ 0.1)
4. 4. O’Conner formula: Weight × (1 + (0.025 × number of reps))

If you're looking to build muscle and increase your one-rep max, consider lifting incrementally heavier weights over a period of several weeks until you gradually work your way up to a higher 1RM.

1. 1. Start at 70 percent: Start by lifting a weight that is 70 percent of your 1RM for 10–15 reps.
2. 2. Increase to 80 percent: After becoming comfortable with the previous weight, increase the weight to 80 percent of your 1RM and practice lifting that amount for 5–10 reps. Practice with this weight for a few weeks.
3. 3. Increase to 90 percent: When you're ready, move up to 90 percent of 1RM for 3–4 sets of 3–4 reps and practice that for a few weeks.
4. 4. Increase to 95 percent: Increase the weight to 95 percent of your 1RM for two sets of just 1–3 reps. This will be a challenging lift, so be sure to use a spotter to avoid an injury.
5. 5. Increase to your 1RM: After you’ve become comfortable lifting 95 percent of your 1RM for multiple reps, try lifting your 1RM weight for more than one rep. At this point, you should be able to lift a slightly heavier weight for a maximum of one rep. Use the help of a spotter or personal trainer to avoid injury when lifting your maximum weight.

If you have a previous or pre-existing health condition, consult your physician before beginning an exercise program. Proper exercise technique is essential to ensure the safety and effectiveness of an exercise program, but you may need to modify each exercise to attain optimal results based on your individual needs. Always select a weight that allows you to have full control of your body throughout the movement. When performing any exercise, pay close attention to your body, and stop immediately if you note pain or discomfort.

To see continual progress and build body strength, incorporate proper warm-ups, rest, and nutrition into your exercise program. Your results will ultimately be based on your ability to adequately recover from your workouts. Rest for 24 to 48 hours before training the same muscle groups to allow sufficient recovery.

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