Workout Guide

How to calculate your 1RM (One Rep Max)?

The progress of exercising reps varies from one person to the other because it depends on the weight lifting ability. One Rep Max is the maximum weight that an individual can lift for a repeated exercise. Multiple reps are done by people while working out whether they do bench press, butterfly chest exercises, biceps training or wings exercises.

Calculation logic behind 1RM

Various formulae are used to determine 1RM but the most common one is called Brzycki formula. Here is the general elaboration of this logic.

1RM = weight / (1.0278 – 0.0278 × reps)

To get a feel of the how this works, considering an example would be a good approach. Suppose that you have a weight of 120 kilos for which the 1RM has to be determined. Simply insert the weight value in the above formula. 

1RM = 120 / (1.0278 – 0.0278 X reps). 

The number of reps is the frequency for which you were able to lift the desired weight without any problem. Consider that the value is 3 in this case. Hence, we have the following interpretation.

1RM = 120 / (1.0278 – 0.0278 X 3)

1RM = 132 kg

Correct calculations through a 1RM calculator

Although there is a formula to determine 1RM and one can use it by inserting appropriate values. have built a very user-friendly 1RM Calculator. It calculates One Rep Max very quickly. However, using a calculator proves to be a better alternative due to several reasons. 

  • Accuracy

It is important to know about the correct 1RM value for best fitness results. Inserting values in the formula is possible but not the best way out in terms of accuracy. Using a 1RM calculator works well because mistakes are not made while the values are being determined. At times, you may enter the wrong values in the formula which would result in the wrong values being produced. As a result, your fitness progress would go in the wrong direction.

  • Quick Results

The conventional method of inserting values in the formula does not work in terms of time efficiency. For some people, several minutes would be needed to produce the results. This is not the case when you are using a calculator.

  • High standard 1RM calculators are time efficient by all means. You do not have to sit down with a pen and paper to perform calculations. All you have to do is insert the appropriate values and the one rep max value will be determined. The use of an automated tool helps in saving precious time.
  • No mathematical knowledge required

Everyone does not have command on formulae and insertion of values. You can end up wasting time and still getting incorrect results by using manual calculation methods. The 1RM calculator can be used by people easily even if they do not have appropriate mathematical concepts. There is no need to be an expert at multiplying or dividing values if you are using a one rep max calculation tool.

Steps of using a standard 1RM calculator

There is nothing difficult about using the 1RM calculator. The process comprises of few simple steps that are completed in short spans. Here is what you need to do for determining the one rep max value using this calculator.

  • Enter the value of weight lifted and select unit

How much weight do you plan to lift for the 1RP exercise? This completely depends on the ability that an individual has. It is the first input which users have to enter. After that, you need to select the unit of weight. Apparently, most tools offer two options (lb and kg). Users can make a selection according to the unit they are comfortable with.

  • Enter the number of repetitions

How many reps do you plan to you? This is the second and last input that has to be entered. Once both inputs have been entered, move ahead towards the result generation stage.

  • Understanding the outputs

The calculator would produce the output in tabular form comprising of three fields. The first one is number of repetitions which highlights the number of times an exercise has been repeated. The second is weight lifted. This count declines as the repetitions increase. Similarly, the third field is called percentage of IRM. It usually shares a relationship of inverse proportionality with the number of repetitions.

  • Looking at an example

Further understanding of the inputs and outputs can be understood by looking at an example.

  • Suppose that the weight is 130 kilos and number of repetitions is 3. Enter these values and click the “calculate one rep max” button. This would generate the output table. Once you have a look at different rows, it would be easier to understand how the results vary. For instance, the first repetition would have a weight lifted of 137.7 kg and 1RM of 100%.
  • These values will decline once the number of repetitions increase. This is because both “lifted weight” and “1RM percentage” share inverse relationships with it. For instance, if we have a look at the 6th repetition, the weight lifted would be 118.5. In comparison to the first repetition where the weight lifted was 137.7 kg, this value is lesser. Similarly, the 1RM percentage at the 6th repetition will be 86% which is lesser than 100%.

If you are seeking a good tool, the 1RM calculator is one of the finest option. It has a robust and strong programming algorithm due to which correct results are generated at a very fast pace. It is an online tool used by several weight lifters monitoring their reps.

Confirmation of 1RM values through physical testing 

A good calculator would never produce incorrect results but still, actual testing can help in getting a confirmation. You would know your ability when you perform the reps at the gym. You can use the following steps for this activity.

  • Keep the set of results printed on paper in front of you before starting the reps.
  • Take one rep at a time in terms of comparing results. For instance, let us reconsider the above example where we had “lifted weight” of 130 kilos and “number of reps” to be 3. As per the results, you should be able to lift a weight of 137.7 kg with 100% one rep max. After completing the first rep, compare your performance with what you have on paper. 
Mick Foley
the authorMick Foley
An aspiring Pro Wrestler, Mike loves working out in the gym and attending MMA classes. When not lifting weights, Mike will most probably be lifting his PS4 controller. He writes for Resistance Pro to share all that he has learnt.