Calculating your 1 rep max

In weight training or bodybuilding you will often get asked questions like “what do you bench”? or “what can you lift”? These are obviously quite ambiguous questions but what is meant by them usually is “what is your repetition maximum on the bench press or other big lifts”?


Now most people who have trained for a long time will have worked out their one repetition max by simply attempting heavy weights that they can only just lift once and when they succeed at a weight but cant do any more than that then they have achieved their 1 rep max. However there are a lot of trainers who don’t know their one rep max lifts on any exercise. This could be because they have no interest in knowing or more likely because they don’t feel comfortable in trying such a heavy lift. They may not have a spotter or it may be that they feel the strain on the body and risk of injury is too great. Doing a 1 rep max does put a lot of strain on the muscles and joints as it is in essence the largest possible amount of force your body can deal with in a concentric contraction.


I personally think that knowing your 1 rep max is important. It is a goal that you can aim to improve on over time with your training. To increase your 1 rep max on a lift is a very measurable and sensible goal in my opinion as it is the test of true total strength on a particular movement. There are different ways to train to improve 1 rep max lifts and strength training in any sense can be very fun and beneficial.


So back to the main problems that people have with testing their one rep max. Not having a spotter or someone to aid them in the lift should something go wrong is the main one in my opinion. I will admit that on most of my 1 rep max attempts I am not able to complete the lift. Without a spotter I would be stuck under the bar on the bench press quite regularly. This is not due to lack of ability in correctly predicting a 1 rep max but more down to a need to keep testing until I fail at the lift. For example if I lift 100kg easily then I will try 105kg. If 105kg is a struggle but I get it to full lockout I will not think “ok 105g is my 1 rep max”, I will try for 107kg or 110kg as that may in fact be my 1 rep max. This is where it becomes dangerous to do on your own.


There is, however, a solution to this problem. You can work out your one rep max using equations. This is not going to be your actual 1 rep max until you test it out but it is a very good indicator and will help you to know roughly where your 1 rep max is.


The equation is:



This equation may look a bit confusing but it really is quite simple.

‘r’ stands for number of reps performed.

‘w’ stands for weight.


So lets say that you bench press 100kg for 10 reps (just to be nice and easy).


You will need to divide the number of reps by 10.

This = 0.33

Add 1 to this number.

This = 1.33

Multiply this by the weight you used.

This = 133kg.


So if you can bench press 100kg for 10 reps, your 1 rep max is roughly 133kg.


So next time you are in the gym and have someone to spot you that you trust I recommend giving your 1 rep max a go. Work it out using this equation so that you have a rough idea of what to go for, then push pull or squat as hard as you can and get a 1 rep max down.



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