How to Determine a 1RM

How to Determine a 1RM (FI)

If you goal is to get stronger in the gym, your 1 rep max (1RM) of a given exercise is an important number to know and understand. The 1 rep max can be defined as the maximum amount of weight that can be lifted for a given exercise for a single repetition. Many training programs, such as Wendler’s 5/3/1, base the weights to used for the training program off of your 1RM, so if following a training program which uses 1RM’s to determine training percentages, the 1RM is an important number to know and understand. A 1RM is also a useful gauge to determine whether or not you have made strength gains from weight training. Being predicted and/or to be able to squat 400 lbs under the same conditions as 375 lbs is objectively better, and testing/knowing your 1RM for a variety of exercises is critical in tracking your progress in the gym.

There are two main ways to determine a 1RM, and that is either through direct testing or submaximal estimation.

Directly testing your 1RM

This is definitely the simplest method to determine your 1RM, which is to simply go to the gym and see how heavy you can get a single repetition! This is also the most accurate option for obvious reasons.

There are a few factors which can influence your ability to successfully hit your 1RM though.

First, if any exhaustion is present, and glycogen stores are depleted, any 1RM that is achieved will likely be lower than is actually possible if energy levels were optimal. The best way to counter this is not to exert yourself too hard before training in order to keep energy levels right, and having a meal or peri-workout drink to max out glycogen levels before hitting the gym is also helpful.

Secondly training fatigue might be encountered. Training fatigue is fatigue that accumulates over the course of a training block for a variety of reasons, but ultimately what it does is reduce maximal force output and strength. My 1RM in the squat might be 400 lbs, but if training fatigue reduces that 1RM by 5%, then my squat 1RM is only 380 lbs + fatigue. Luckily, it is fairly easy to reduce training fatigue. Reduce training volume over the course of 1-3 weeks while still working the exercise movement 2-3x a week (to keep the CNS active) and most if not all training fatigue will be eliminated. This is basically what a powerlifter or olympic lifter will do in prepartion for an upcoming meet in order to hit new records. The longer the training period the longer the deload will have to be. You can expect to hit a 1RM 4-8% higher than before if training fatigue is successfully eliminated. You can read a further in-depth explanation of fatigue over at Juggernaut Training.

Lastly, an inefficient warm up will reduce the amount of weight able to be lifted during a 1RM. When warming up, it is generally best to increase the weight of the exercise while simultaneously reducing the number of repetitions performed, for example:

Working up to a 1RM

Efficient Warmup

1st set – 135 lbs for 10 reps

2nd set – 185 lbs for 7 reps

3rd set – 225 lbs for 5 reps

4th set – 275 lbs for 3 reps

Working sets

315 lbs for 1 rep

335 lbs for 1 rep

355 lbs for 1 rep (1RM)

Inefficient Warmup

1st set – 135 lbs for 10 reps

2nd set – 185 lbs for 10 reps

3rd set – 225 lbs for 10 reps

4th set – 275 lbs for 8 reps

Working sets

315 lbs for 1 rep

335 lbs for 1 rep (FAILED)

325 lbs for 1 rep (1RM)

The inefficient warm up method performs too many reps at increasing weights instead of tapering down the reps as the weights get heavier, so when it comes time to perform a 1RM, less weight was able to be lifted compared to the efficient warm up method. Insufficiently resting in-between sets will also reduce your ability to hit a true 1RM. This is a hypothetical example, and the best way to determine how you most efficiently warm up in preparation for an exercise is to mess around with the numerical increases in weight between warm up sets and the taper of repetitions for warm up sets until you find a combination which best suits you.

Certain supplements can also increase your 1RM immediately or in a very short period of time, such as caffeine, but it is best to use the supplements which have diminishing returns with continued use only occasionally, such as during weightlifting meets.

Submaximal 1RM Estimation

The submaximal 1RM estimation method is a method to determine a 1RM using a XRM (X amount of reps). With a variety of equations to choose from, you record the maximum number of reps able to be completed at a certain weight, using a weight heavy enough to keep the maximum number of reps able to be performed ideally 10 or below, and plug in the variables of exercise weight used (w) and reps (r) to calculate your 1RM.

For beginner lifters, the submaximal 1RM estimation is the safer, less nerve wracking, comfortable option, and the submaximal estimation method is also a great way to gauge progress when following a training program where you won’t have the opportunity to hit a 1RM.

The submaximal 1RM estimation method still has to grapple with the possible low energy, training fatigue, and inefficient warm up factors, but it is a great way to track 1RM progress without actually having to perform a 1RM, which can use up an entire training day. If you are going to use a training set to submaximally determine a 1RM for an exercise, use the first working set for that exercise rather than the last as you will be the most fresh on the first set.

There are a variety of equations which can be used to determine a 1RM using submaximal loads, and listed below are the names and equations of a few popular methods:

Epley Formula

1RM = w \left ( 1 + \frac{r}{30}\right )


1RM = w \cdot \frac {36}{ \left ( 37 - r \right ) } = \frac{w}{ \left [ \frac{37}{36} - \left ( \frac{1}{36} \cdot r \right ) \right ] } \approx \frac{w}{ \left [ 1.0278 - \left ( 0.0278 \cdot r \right ) \right ] }


1RM = \frac{100 \cdot w}{101.3 - 2.67123 \cdot r}


1RM = w \cdot r^{0.10}

Mayhew et al.

1RM = \frac{100 \cdot w}{52.2 + 41.9 \cdot e^{-0.055 \cdot r} }

O’Conner et al.

1RM = w \cdot (1 + 0.025 \cdot r)


1RM = \frac{100w}{48.8 + 53.8e^{-0.075r}}

r = Repititions performed; r ≥ 1

w = weight

In the following graphic, all of the different equations have been inputed and a hypothetical 1RM of 100 pounds is used. The weight (and %RM) calculated for each repetition amount is listed for each equation, and a final average of all the equations is listed at the bottom. The average of the seven equations is likely the most accurate method to use in determining your 1RM using submaximal loads rather than any one specific 1RM equation.

1RM equations

Considering the 1RM used for all of these equations is 100 (units don’t matter), the various weights able to be lifted for each rep amount for each equation also equal a %RM for the given rep amounts. So, at 81% of your 1RM for the Epley equation, you should be able to perform 7 reps.

Looking at the above equations, the Epley equation seems to best correlate with my anecdotal 1RM estimates based on time spent training, but everyone responds different to 1RM’s, and the equation which might best represent me might poorly represent you. As a result, I like to take an average of the equations to determine my 1RM using a submaximal estimation.

ExRx also has a 1RM calculator webpage which is a good resource to use in determining your 1RM.

Learning how to calculate a 1RM is an important weight training skill, and knowing and tracking the progression of your 1RM for a variety of exercises such as the squat and deadlift will allow you to make better progress in the gym and set clearer weight training goals. Just make sure to jot down your 1RM’s in your training journal so you don’t forget them!


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Stefan Burns

Stefan Burns

Fitness, nutrition, and powerlifting buff. Created Strength Cooperative as a way for hardworking, natural lifters to share advice on how THEY got results in the gym.
Stefan Burns

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