Deadlift 1 Rep Max (1RM) Calculator: With 9 Formulas

The following Deadlift 1 Rep Max calculator uses 9 different 1 Rep Max Formulas. Of these the most widely used are the Brzycki and Epley formulas; These equations - as well as the others - are broken down below.

Calculator Usage: Our calculator is simple and easy to use - select your formula, input your the weight you deadlifted, and the number of repetitions you deadlifted said weight for (max of 12 for accuracy).

Deadlift 1 Rep Max Calculator

*Note: These formulas work with both metric and imperial units. Meaning, you can input your weight in Pounds (lbs) or Kilograms (kgs); The output number will also be in your preferred unit.

Weightlifting One Rep Max Formulas

Not all one-repetition maximums (1RMs) are calculated the same, and numerous formulas have been developed over the years to try and create the most accurate estimation. 

While the majority of 1RM formulae are for general resistance exercises and require the same kind of variables, some are geared towards specific exercises or types of weightlifters - and a few will even require different inputs, other than simply weight and repetitions.

Which 1RM Formula is Most Accurate?

There is no specific one-repetition maximum formula deemed to be the most accurate, as they all have their specific uses and as such will be more accurate than others within specific contexts.

For general weightlifting 1RM estimations, Epley and Brzycki are a good starting point.

Note: All of these formulas are included in our calculator above. You can alternatively feel free to do the math and plug your values in for Weight (W) and Repetitions (R) below.

The Brzycki Equation

Perhaps one of the most common 1RM formulas is referred to as the Brzycki equation - after its creator, Matt Brzycki.

The Brzycki equation requires only two variables (volume and weight) and is meant to be used for practically any free weight resistance exercise, hence its widespread usage.

Equation:

1RM = W x (36 / (37 - R))

W or weight is the amount of weight lifted in pounds or kilograms.

R is the volume or number of repetitions performed with said W or weight.

The Epley Formula

The Epley formula is another highly popular 1RM equation that is applicable to weightlifters of all disciplines and goals. It is considered to be (at least) on-par with the Brzycki equation in terms of accuracy.

Unlike other formulas, Epley’s features an inverse coefficient relationship with the variable R, or the number of repetitions performed within the test set.

This is further made distinct by the assumed linear relationship between weight and volume, and as such makes the Epley formula somewhat less accurate for weightlifters near the elite levels of development.

Equation:

1RM = W x (1 + 0.0333R)

W or weight refers to the gross load of the exercise, either in pounds or kilograms.

R is the volume of the set performed with the aforementioned weight.

The Adams Formula

While one may think that the Adams formula is practically the same as Epley’s formula - the two are distinct by way of their coefficients, as the Adam’s formula uses 0.033, which will translate to a slightly lower one-repetition maximum (1RM) estimation in comparison.

Equation:

1RM = W x (1 + 0.033R)

W refers to the weight used during the set.

R is the number of repetitions performed using said weight.

The Landers Formula

Unlike other formulas used to calculate a one-repetition maximum, the Landers formula will account for the lifter’s own body weight in its estimations.

This is achieved through the use of an additional coefficient, and is particularly useful for powerlifting or strongman athletes where body weight may play a pivotal role in performance.

Equation:

1RM = (100W) / (101.3 - 2.67123R)

W refers to the amount of weight lifted in the set, of which will be multiplied by 100 and used as a percentage of the lifter’s own body weight.

R refers to the repetitions performed with W or weight.

The Berger Formula

The Berger formula is considered one of the easiest 1RM calculations to perform, as it only features a fixed constant to estimate the one-repetition maximum load in reference to the repetition variable. 

While simpler and far less mathematically-intensive, the Berger formula is also considered somewhat less accurate than other popular 1RM formulas.

Equation:

1RM = (W x R x 0.033) + W

W or weight is the gross load of the performed set.

R refers to the number of repetitions within said set.

The Wathen Formula

The Wathen formula is unique among 1RM equations by its attempt to estimate the rate of muscular fatigue as the lifter performs their testing set. 

This causes the formula to trend towards lower estimations than most other popular methods of 1RM calculation - although there is evidence that it is somewhat more accurate for novice or intermediate lifters, as well.

Equation:

1RM = (100 x W) / (48.8 + 53.8 x e^(-0.075 x R))

W refers to the amount of weight lifted per repetition

R refers to the number of repetitions performed with said weight.

“e” is a mathematical constant (Euler's number) estimated to be 2.71828, accounting for muscular fatigue over the course of the set.

The Mayhew et al. Formula

The Mayhew et al. formula is another one-repetition maximum calculation known for being applicable to weightlifters of all disciplines and levels of experience, featuring comparative accuracy to most other modern formulae.

Unlike most other formulas, the Mayhew formula is primarily used with kilograms, rather than pounds; Conversion may be necessary.

Equation:

1RM = ( W x (0.025 x R + 0.75))

W or weight refers to the weight of each repetition performed in kilograms.

R is the number of repetitions performed within the testing set.

The Lombardi Formula

The Lombardi formula is another widely-applicable 1RM estimation formula made distinct by its assumption of non-linear correlation between the given variables (volume and weight, respectively); This is shown in its use of 0.1 as an exponent value - far lower than other formulas of the same variable requirements.

In turn, the Lombardi formula will return a lower one-repetition maximum load in comparison - especially for endurance athletes and other lifters with significant muscular endurance.

Equation:

1RM = W x ( R ^ 0.1)

W equates to the amount of weight lifted per repetition.

R is the number of repetitions that were done during the testing set.

The O’Connor et al. Formula

In comparison to other modern formulae, the O’Connor et al. formula features reduced accounting for volume through a lower coefficient value (0.025).

This means that volume is taken less into account than other formulas would do, and as such will result in a higher 1RM estimation for high R variables.

In the end, the O’Connor et al. formula will return a higher one-repetition maximum estimation than most other formulae - especially for weightlifters who are able to perform a high number of repetitions with their testing weight.

Equation:

1RM = W x (1 + (0.025 x R))

Which 1RM Formula is the Best?

In truth, there is no single “best” one-repetition maximum (1RM) formula, as each different equation features its own set of unique strengths and use-cases.

Some formulas (like the Lander’s formula) are more appropriate for strength athletes or those with a particularly small test set volume, whereas others (such as Lombardi’s formula) are more appropriate for lifters performing movements with less weight but more volume.

For the most accurate estimation, lifters should pick one primary formula to base their assumptions on - and average it out with the use of several other formulas.

A good starting point is the Brzycki formula, as it is considered to be among the most general and accurate calculations available.

How Accurate are These 1RM Calculators?

Estimations made through 1RM calculators are limited in accuracy by two factors; statistical deviation and biological differences between individuals.

Biological Variation

Nearly all one-repetition maximum formulas are based on data from a specific set of individuals, be it a sample group of untrained mixed-gender adults or a cohort of highly advanced college-aged strength athletes. 

In all cases, it is likely that the lifter performing such calculations is not biologically identical to the sample population with which the formula is based on, resulting in minor inaccuracies of 1RM estimation.

Physiological characteristics like age, gender, muscle fiber composition, neurological adaptation and even previous training specificity can all gear a lifter towards performing less or more than their estimated 1RM, and as such it is important to remember that 1RM formulas and calculators produce an estimation, not an absolute.

The Limits of Variable-Based Estimation and Other Inaccuracies

In loose connection to the data sets in which these formulas are based, mathematical limitations also play a part in the accuracy of 1RM calculators.

First is the fact that said data set is limited by the scope of the study that produced it; be it errors in sampling methodology, a limited sample size or even the personal interest of the research team.

Furthermore, it has been well-established that weight and volume are two training factors that share a nonlinear relationship - of which is an assumed basis of many 1RM formulas, further affecting their accuracy. 

In addition, the actual variable data input by the lifter themselves may be inaccurate, as they may be performing their test set while fatigued, with poor form, or with some other factor affecting their performance so as to skew the volume and weight that is inputted.

Why 1RM Calculators Have a Maximum Number of Repetitions

One-repetition maximum calculators (and their subsequent formulas) have a limit to the number of repetitions they can calculate with for a reason; weight and volume is assumed to have a significant correlation, be it linear or nonlinear.

This can cause test sets with very high numbers of repetitions to produce inaccurate estimations, as performing 10 repetitions for 100 pounds does not necessarily equate to being able to perform 20 repetitions with 50 pounds, for example.

Our calculator uses 12 as a baseline.

In addition, the majority of weightlifters are advised not to perform extremely high volume sets with any significant (over 60% of 1RM) amount of resistance, as doing so may cause tissue irritation and even injury.

A Few Tips and Reminders When Performing a 1RM

As a reminder, remember that performing any sort of exercise at your absolute maximum effort is dangerous - especially with free weight exercises. If you have a history of injury or health conditions, it is far better to avoid manual testing of your one-repetition maximum altogether. 

In addition, regardless of whether you are completing a working set or your 1RM, every repetition should be performed with perfect form and technique. Some exercises like the stiff-legged deadlift or thumbless-grip bench press are especially dangerous when performed for a 1RM, and can result in serious injury.

Finally, it is also important to keep in mind that the results of one-repetition maximum formulas are not true to real life, and that the results of 1RM calculators are meant to be a rough - although somewhat accurate - estimation.

References:

1. Haff G.G., Triplett N.T. Essentials of Strength and Conditioning. Human Kinetics; Champaign, IL, USA: 2015.

2. LeSuer, Dale A.; McCormick, James H.; Mayhew, Jerry L.; Wasserstein, Ronald L.; Arnold, Michael D.. The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift. Journal of Strength and Conditioning Research 11(4):p 211-213, November 1997.

3. Macht, Jordan W.; Abel, Mark G.; Mullineaux, David R.; Yates, James W.. Development of 1RM Prediction Equations for Bench Press in Moderately Trained Men. Journal of Strength and Conditioning Research 30(10):p 2901-2906, October 2016. | DOI: 10.1519/JSC.0000000000001385

4. Schoenfeld BJ, Grgic J, Van Every DW, Plotkin DL. Loading Recommendations for Muscle Strength, Hypertrophy, and Local Endurance: A Re-Examination of the Repetition Continuum. Sports (Basel). 2021 Feb 22;9(2):32. doi: 10.3390/sports9020032. PMID: 33671664; PMCID: PMC7927075.