1 Rep Max Calculators: Find Your 1RM

The term one-repetition maximum (1RM) refers to the gross amount of weight a particular exercise is performed at when the lifter is at their absolute physical limits. It can be thought of as their maximum muscular force output in a single given training movement.

This is often used in regards to resistance training exercises like the bench press, deadlift or squat, and isn’t exactly applicable to aerobic exercises or resistance movements that aren’t measured in repetitions.

1 Rep Max Calculator

Note: The above calculator uses the Brzycki formula.

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, the Brzycki equation is a good starting point.

If you’re looking for calculators that utilize more than the Brzycki formula to ascertain a 1 Rep Maximum estimation, you can find specific calculators below:

How is a 1RM Calculated?

One-repetition maximums are calculated by taking the amount of weight a lifter can perform for more than a single repetition (generally, fewer repetitions are more accurate – most calculators stop being accurate after 12 reps), and inputting said weight and volume as variables within a formula (above).

Multiple formulas have been developed over the years, all of which will return different estimated 1RM sums – and it is up to the lifter themselves to decide which formula is most appropriate to base their programming on.

Alternatively, if the lifter does not want to calculate their 1RM themselves – or make use of the calculator above – they may find their one-repetition maximum the manual way. 

This is done simply by performing single-repetition sets with progressively increasing weight until reaching the point of approximate muscular failure.

If you’re interested in doing the above equation for yourself, it is as follows:

1 Rep Max = Weight Lifted * (36/(37-reps lifted))

Why are 1RM Calculators and Formulas Better Than Manual One Rep Max Testing?

Unless competing in powerlifting or strongman events, the majority of individuals are not prepared for lifting an amount of weight too heavy for their muscular and neurological capabilities. Doing so can easily result in injury, be it from poor form adherence due to strain or simple overloading of soft tissue.

This is especially true for novice or intermediate weightlifters, whose bodies have yet to fully adapt to resistance training and as such are at higher risk of injury when performing very heavy (1-2 repetition) sets.

1RM calculators circumvent this risk by taking the data from a less risky set (more than 1 repetition) and estimating how heavy the lifter’s one-repetition maximum could be – all without the need to actually perform a one-repetition maximum lift.

The disadvantage to this is that one-repetition maximum formulas may return an inaccurate number, both as a result of biological variability between lifters and because of mathematical deviation.

How to Use Your One Repetition Max (1RM) for Training Programming

Once an exercise’s one-repetition maximum has been determined, the lifter may take a percentage of this estimated number to decide the volume and resistance of their training programming.

For example:

If the estimated one-repetition maximum is 100 pounds (approximately 45 kilograms), and the lifter desires muscular hypertrophy, they will structure their volume and resistance by performing rep schemes at these various percentages.

Note: The above calculator can ascertain these values for you. Assuming your goal is hypertrophy, you’d select 12 reps and input your weight lifted. Eg. if you lifted 225 lbs for 4, your 12 rep max is roughly 172 lbs.

Not all lifters have the same physiology or training methodology however, and these numbers can often vary between individuals. 

Some lifters will be able to perform a higher amount of volume with a greater percentage of their 1RM than others, and as such it is beneficial to seek out personally-tailored coaching if maximum program optimization is desired.

For Strength Development

Strength development programs are characterized by sets of 80-100% of a one-repetition maximum for 1-5 repetitions each. 

While strength development is somewhat more technically complex than muscular endurance or hypertrophy, the majority of novice-to-advanced weightlifters can stick to linear progression through low volume sets and a high percentage of their estimated one-repetition maximum.

This, of course, is for primary compound exercises and not accessory or secondary movements.

For Hypertrophy

Bodybuilding and hypertrophy-focused programs will generally follow a trend of 60-80% of a one-repetition maximum, with volumes of 8-12 repetitions per set.

If the estimated one-repetition maximum is for a primary compound exercise, lifters wishing for muscular hypertrophy often take to moderate volume schemes with a summarily moderate load as well. 

Isolation exercises however, do not follow the same trend, and are commonly performed for up to 20 repetitions if needed.

While the sports science community is still researching the veracity of this idea, the established concept of a “repetition continuum” appears to agree with the tenets of moderate-load and moderate-volume for fiber-specific muscular hypertrophy.

For Local Muscular Endurance

Marathon runners, martial artists and other forms of athletes will often perform repetitions in excess of 15 per set, with loading of below 60% of their estimated one-repetition maximum.

The leading theory behind such a high amount of volume per set revolves around physiological adaptations (capillarization, mitochondrial population, metabolic efficiency) to high volume under load, and is primarily seen as a localized response – meaning that the adaptations will only take place in the muscles that are being trained.

Frequently Asked Questions (FAQ)

How Much Should Your One Rep Max Be?

The one-repetition maximum a lifter is capable of will vary between different individuals, and there is no hard-set value with which one should compare themselves to. 

Factors like training specificity, intrinsic physiological characteristics and even equipment usage can all affect the 1RM of a lifter, and as such it is meaningless to compare oneself to another in this context.

Is Using a 1RM Calculator or Testing it Yourself Better?

There are advantages and disadvantages to either approach. Calculating is easy and safe, but may be inaccurate. Manual testing could potentially be dangerous, but is the only way to truly establish a 1RM.

For the most accurate measurement, it is best to first estimate your 1RM through the use of a calculator, and to then test it out yourself at the gym – adjusting the weight by adding slightly more or slightly less as needed.