Bench Press 1 Rep Max (1RM ) Calculator: With 7 Formulas

This bench press 1RM calculator makes use of the 7 most useful one-repetition maximum formulas - all of which are considered to be suitable for the needs of most weightlifters and athletes. 

Calculator Usage: Our bench press 1 RM calculator is simple and easy to use – select your formula, input your weight benched, and the number of repetitions you benched said weight for (max of 12 for accuracy).

Each individual formula possesses unique coefficients and applicability, and as such have been outlined below for the convenience and learning of the lifter (below).

What are One Rep Max Formulas?

A one-repetition maximum or 1RM formula is simply a calculation with which a lifter will determine how much weight can be lifted at maximum effort for a single repetition. 

This will generally require that the lifter already know how much they can lift for a higher number of repetitions, such as performing the bench press for 5 repetitions of 100 pounds (45 kilograms).

One-repetition maximum formulas differ in terms of their coefficients, the method in which they reach the estimated 1RM and even the required inputs or variables from the lifter themselves. 

This leads to some formulas being more appropriate for certain types of exercises or groups of individuals than others - and as such it is a good idea to first study which formula is most suitable for your needs before altering your training program.

While the Epley and Brzycki formulas are the most popular, they are not specifically geared towards the bench press and may return a more inaccurate number than the Wathan or Mayhew formulas.

Why are One-Repetition Maximum Formulas Important?

Identifying 1RM (regardless of which exercise) allows the lifter to better understand the approximate numerics of their physical limitations, providing the ability to structure their training program in a manner that is more than simply inefficient guesswork.

In practice, identifying the 1RM of a particular exercise can allow the lifter to plot progression schemes, identify whether they are making progress at a steady rate and even their supposed training experience level, when calculated alongside their own bodyweight and age.

Can One-Rep Maxes be Tested Without a Calculator?

Although manual testing of one-repetition maximums is considered to be more accurate than volume-and-weight calculations, it is not recommended with the bench press or if the lifter is only of a novice level, as both cases can result in injury.

The Bench Press 1RM Formulas

1. Wathan Formula

The Wathan or Wathen formula (known by other names as well) is noted for being particularly useful for determining the 1RM of the bench press due to its inclusion of estimated rate of muscular fatigue by way of “e” or Euler’s number as a constant alongside an assumed exponential relationship between volume and load.

In this formula, W refers to the weight loaded per repetition, with R referring to the volume of repetitions.

Equation:

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

2. Mayhew et al. Formula

The Mayhew et al. calculation is a generalist formula with comparative applicability and accuracy to other popular formulas - however, it is noted in some reviews to be particularly applicable for estimating bench press one-repetition maximums among novice and intermediate lifters.

In the Mayhew et al. formula, the variable W refers to the amount of weight moved per repetition, with R referring to the number of said repetitions.

Equation:

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

3. Epley Formula

Perhaps one of the most commonly employed formula for estimating a 1RM - the Epley formula simply involves multiplying load lifted by a coefficient aligned with the number of repetitions that are performed during the testing set.

In this formula, W refers to weight and R refers to volume.

Equation:

1RM = W x (1 + 0.0333R)

4. Brzycki Formula

The Brzycki formula is one among the most widely used modern 1RM formulas available, as it is not only relatively mathematically simple, but also applicable to all resistance exercises and individuals of all types.

In the Brzycki formula, W refers to weight lifted with each repetition, and R refers to the number of said repetitions.

Equation:

1RM = W x (36 / (37 – R))

5. Lander Formula

The Lander formula is unique in its way of accounting for the lifter’s body weight in its estimations - meaning that a further coefficient is included into the equation. This quirk of calculation makes the Lander formula particularly useful for weightlifters who participate in weight class denominated sports, such as powerlifters.

In this formula, W refers to the amount of weight that is lifted per repetition, where it is multiplied by 100 and a percentage is subtracted so as to assume the lifter’s own weight. 

Furthermore, R refers to the volume of repetitions performed.

Equation:

1RM = (100W) / (101.3 – 2.67123R)

6. Lombardi Formula

The Lombardi formula is another generalized 1RM calculation with a unique assumption of non-linearity between volume of repetitions and the weight lifted with each repetition, meaning that it will tend to return less accurate values for individuals with significant muscular endurance.

The variables of the Lombardi formula are otherwise much the same as other formulas, with W referring to weight and R referring to volume of repetitions in the set.

Equation:

1RM = W x (R ^ 0.1)

7. O’Conner et al. Formula

In comparison to other modern formulas, the O’Conner formula approaches the 1RM problem by viewing volume in a far less important light, featuring a coefficient value of 0.025 instead.

This skews the calculation more towards high volume sets, causing the formula to return a 1RM result that is far higher as the volume of the test set is also input at a high number. 

As always, the variable W refers to weight lifted per repetition, and R refers to the number of repetitions.

Equation:

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

What’s the Best Formula for a Bench Press 1RM?

In truth, no 1RM formula is the “best” formula for a multitude of reasons, physiological and mathematical variations notwithstanding.

However, quite a bit of academic text has been written on the subject, and as such has led to some debate as to the most applicable calculation - or whether calculating based on regressive equations of volume and weight is even applicable at all.

Fortunately, for the sake of simplicity, most studies conclude that the most applicable of formulas are the Wathan et al. formula, and the Mayhew et al. formula, as is outlined in a review of the Journal of Sports Science and Medicine; “they reported that only the equations of Mayhew et al. and Wathan successfully predicted the 1-RM for the bench press.“

How to Use Your Calculated Bench Press 1RM

Once you’ve performed your testing sets and calculated a bench press 1RM, you may be wondering how best to take advantage of this information.

Apart from asking your athletic coach for advice, knowing your current 1RM will allow you to progressively plot out your training program, as well as estimate when you should reach your training goals.

Estimating Program Volume

The majority of resistance training programs do not use one-repetition maximums in their workout sessions. However, they can base assumed volume and weight lifted on said 1RM and the desired training stimulus of the program.

This is achieved by basing the lifter’s repetition scheme and resistance on their 1RM, with hypertrophy generally being 60-80% with 8-12 repetitions per set, strength being 80-100% for 1-5 repetitions per set, and endurance being below 60% and over 15 repetitions per set.

For example, if you wish to induce hypertrophy efficiently, you may perform the bench press with 8 repetitions of 80 pounds (36 kilograms) out of your 100 pound (100 kilograms) 1RM.

Predicting Linear Strength Progression

Although it is true that lifters will progress due to a variety of inestimable factors, it is possible to get a rough timeline of when a lifter will reach a certain amount of weight lifted, based on their current rate of progression and their 1RM.

To make this easier, lifters will generally base such assumptions on their current training experience level. 

Novices can be said to add as much as 5 pounds or 2.3 kilograms per several days, whereas intermediate level lifters 5 pounds or 2.3 kilograms per week, with advanced lifters possibly progressing at the same rate over the course of a month, and so on.

A good example of this is a novice can be expected to add up to 15 pounds or 6.8 kilograms within only a week or two - something that is nearly impossible for an advanced weightlifter. 

In theory, the novice lifter can aim to lift 30 pounds or 13.6 kilograms more on their bench press within the month, whereas the advanced lifter cannot expect such rapid progression.

Keep in mind that tracking linear progression is only a rough estimate, and becomes less accurate as the lifter grows more advanced, or if their recovery and diet are not optimized for strength development.

Estimating Strength “Level” by 1RM and Body Weight

While all lifters differ in terms of physiology and performance, statistical trending has provided a sort of “baseline” with which lifters can assume their level of training experience - allowing them to pick the training methodologies and approaches that are most appropriate for their level of physical development.

This is done by taking the lifter’s 1RM of a particular lift and comparing it to their peers in age, gender and body weight. 

For example, a male lifter of 180 pounds (81.6 kilograms) is considered to be in the 95th percentile among their peers if their bench press 1RM is over 350 pounds (158.7 kilograms) - placing them firmly in the “advanced” or “elite” category, so to speak.

Clearly, the sort of training and expected progression from such an individual would be distinct from one who is in the bottom 5th percentile of their peers, hence the importance of 1RM testing in individualized training programming.

Are Calculated One Rep Maxes Always Accurate?

As was mentioned in a previous section of this page, there is no “best” formula - a fact that is evidenced by the imperfect accuracy of all one-repetition maximum calculations.

Though there is no doubting that your calculated 1RM is relatively accurate, it is moreso an estimation rather than a hard-set fact due to differences in physiological variations and the quirks of mathematics.

Should you take the bench press 1RM you’ve acquired from this calculator and punch it into your training program? Absolutely.

But keep in mind that there may be some small deviations when in actual practice and always use a spotter.

Physiological Variations

No two lifters are the same, be it down to differences in muscular attachment points, endocrinological function or even mind-muscle contraction capabilities. 

Unfortunately, the studies with which all one-repetition maximum formulas are based make use of actual samples of real individuals - of which are unlikely to be physiologically identical to yourself. This means that the calculations themselves are likely based on groups of lifters that possess different proportions and biology to you, and can skew the accuracy of your estimated 1RM somewhat.

Furthermore, you yourself may be physiologically different than when you previously performed your testing set. Factors like fatigue, nutrient partitioning and conscious motivation can all affect whether your calculated 1RM reflects an accurate number or not.

Why Calculations are Sometimes Inaccurate - Especially When Weightlifting 

Apart from physiological differences among weightlifters, the math that precedes 1RM formulas can also cause them to be slightly inaccurate.

Factors like whether volume and weight are correlated linearly or not play a big role in the influence of certain variables within a calculation, hence the differences in sums of different formulas.

Even the limits of the data sets with which said formulas are based may be a factor, as total population size, the inclusion of outlier individuals that represent several deviations from the mean, and human error in sampling methodology can be an issue as well.

What Does All This Mean for You?

The fact of the matter is that there is no replacing manual testing in terms of actually finding your one-rep max - but calculators are a close enough estimation that it does not matter in any but the most niche of circumstances.

It is unlikely that the several pounds of deviation from the calculated 1RM will be an important factor in actual training.

So, unless you’re an experienced weightlifter with a firm understanding of the bench press and have a trusted spotter present, it is better to simply use a 1RM calculator, rather than testing it yourself. 

A Note on Manual 1RM Testing and Bench Press Variations

If you’ve chosen to instead test out your bench press one-repetition maximum manually, keep in mind that performing any sort of resistance training at maximal capacity is considered to be dangerous - all the more the bench press, which can easily result in serious injury if the repetition fails.

Ensure that you have a spotter present and ready to help, and that you have taken every possible precaution prior to testing out your bench press 1RM, including speaking to a medical professional beforehand.

Furthermore, if you habitually perform the bench press with the thumbless or “suicide” grip, it is best to change your grip to a far more secure one, as the bar may slip out of your hands. 

References

1. Wathan D. (1994) Load assignment. Essentials of Strength Training and Conditioning. Baechle R.T.Champaign, IL: Human Kinetics

2. Mayhew, Jerry L et al. “Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training.” Journal of strength and conditioning research vol. 22,5 (2008): 1570-7. doi:10.1519/JSC.0b013e31817b02ad 

3. Eston R, Evans HJ. The validity of submaximal ratings of perceived exertion to predict one repetition maximum. J Sports Sci Med. 2009 Dec 1;8(4):567-73. PMID: 24149599; PMCID: PMC3761544.

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.