T Nation

5/3/1 1RM Calculation

Does anybody else think JW’s formula for calculating 1RM from a rep set gives too high a figure? Or maybe it’s to allow for the 1 or 2 reps ‘left in the tank’ as Jim doesn’r reccomend going to failure.

Use the formula on a 1RM and you get a figure of 3.33% more.
Maybe (Weight x (reps-1) x 0.333) +Weight would give a better answer?

(Yes I KNOW I’m over thinking it, I’ made that way! And I KNOW it doesn’t really matter which formula you use, its all about progressing.)

The coefficient is 0.0333 (just a typing mistake I suppose) and yes, your formula gives out your real 1RM when calculated with 1 rep. But on reps 2-10, who gives a shit? I just use it to compare weekly rep PRs and even the original one is good enough for that.

It’s 3,33%, why should it matter when your 1RM can fluctuate more than that depending on the day? And the formula is probably off more than that due to lift/personal variation, so it matters even less.

No formula will be accurate for all persons.

Some can, on a given lift, do 10% more weight for a single than they can for a triple.

Others – this would not be common in PL’ers, but in general – may bomb a weight only 3% higher than their 3RM.

If Wendler’s formula (I haven’t read his e-book, only articles, and so don’t know) is intended to help plan the training program, then the question becomes whether the formula is in fact useful for most users for that purpose. I expect that it is, if that’s the purpose, else Wendler wouldn’t have published it.

But, if it is intended to provide a guess as to what 1RM may be as judged from work at more than 1 rep, but still a low number of reps, then like all such formulas it can only approximate and provide a probably-reasonable guess that usually won’t be drastically far off.

Its away of comparing different weight for different reps and finding which correlates with the best thearetical 1RM.
i.e. is 200kg x 5 reps an improvement on 180kg x 8 reps (JW’s formula says yes).

ssplit: yea a typo, my bad.