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Are 1-Rep Max Calculators Accurate?


Do you guys think they are accurate at all? If so, what is the best formula to figure it out?


I've found them to be accurate within 10-20 lbs.


because I was thinking about starting the 5-3-1 program and was just wondering...

Or should I just plan a workout or 2 to test my one-rep maxes?


Same here. They generally underestimate my max, but it's not that far off.


IMO you're really going to need to test it. I don't max anymore, but when I did I found that they underestimated squat and overestimated bench. I think these things vary too much from individual to individual to accurately calculate.


I don't think the calculators are accurate -- or more precisely, I know they are often wrong -- but if you plug in your values for sufficiently low-rep work, such as say 3 reps, that should be fine for the Wendler.


If for some reason you don't want to actually test your 1rm, here is a (fairly) simple way to calculate it based off higher rep sets..

Forgive me cause this is going to get abit long..

This is obviously a seperate workout dedicated to finding out your 1rm..

Set 1 (S1)- lift a weight that you can do 6-10 reps with.

Have a long break, 5-10 mins.

Set 2 (S2)- lift a weight that you can do 2-5 reps with.

S1 reps - S2 reps= Rep Diff.

S2 weight - S1 weight= Weight Diff.

Weight Diff divided by Rep Diff= Weight Per Rep

Add Weight Diff to S2, for each rep above 1.

That is your 1rm.

So, for example..

S1- 400lbs for 8 reps
S2- 455lbs for 3 reps



55 divided by 5= 11

455+11+11 (one lot of 11 for each rep over 1) = 477

So 1rm would be 477.

This is useful because that rep value of 11 could be used to work out your 1rm any time over the next 6-9 month.

Notice that this is lift specific, the rep value of 11 ONLY applies to your DL, not your other lifts.
Which of course makes it more accurate. But it also means that you have to test each of your lifts seperatly.

This method is much, much more accurate than a 1rm calculator.


As said, the quickest and easiest(...) way to find your 1rm is to just pick up the bar.


If you really need to know your 1RM then you need to plan a workout to find out.

Personally I have never really know my 1RM in any lift as I dont find its worth spending a session finding it out


I agree completely that the method you describe below is considerably better than a calculator that uses only one rep value for the estimation.

However, I have to disagree that having done this calculation and established the per-rep value, that from that point high-rep values (such as weight that allowed 11 reps) will necessarily give reliable values.

One really needs to have low rep values -- preferably as low as 3, but 5 is acceptable -- to get a fairly reliable projection.

It's entirely possible for a person to move to being able to do say 13 reps with the same weight that previously allowed only 11 reps without the 1RM going up substantially at all, though the method you describe would, using your figures, predict a 22 lb increase.

On the other hand, if what was a 3 rep weight now allows 5 reps, the 1RM probably has gone up: or if now the 3RM has gone up by say 20-25 lb, it's even more likely that the 1RM has gone up correspondingly.

The lower the rep value one has to work with, the better the estimation.


Bill Roberts-

You certainly make a good point.

I would definitley suggest using 2-5 reps and then adding the 'extra rep value', as you would do in the orginal testing. For exactly the reasons you pointed out. That's why also the original testing should never be done over 10 reps in the first set, 6-8 would be ideal, 3-4 would be ideal for the second set.

My suggestion that the number is good for 6-9 months is probably abit optomistic, too. Although probably still more accurate than a 1rm caculator.

In light of the OP's question, it's actually irrelevant, becaue he is only needing to know his 1rm for the 5/3/1 program, which will have him doing 1rm's anyway, if I understand it correctly.

But useful for anyone else wanting to use the method I described. I actually "stole" the idea from an article written on this site quite some time ago, sorry I can't remember the author, or I would have just linked it and given them the credit. Although if memory serves their version was abit more long winded...


The Wendler program does have one doing singles (if that is all that one can do with the third set on the 5/3/1 day), but not at the 1RM value. Not even really close to it, actually.

In other words, they are not as heavy as would be possible when rested for an appropriate number of days, and then warmed and led up to properly.

It's actually only 85.5% of 1RM if one used a correct value for 1RM.

As weights increase every 4 weeks, if the increase is faster than the actual increase in 1RM then that percentage will drift higher. But generally speaking it isn't truly maximal.