How do you estimate your 1RM without ever maxing out?

What is a 1RM?

Your max is the heaviest weight you can lift just once. Its real name: the one-rep max, or 1RM. Knowing how many reps you can do at each share of that max is foundational to strength training programs (Nuzzo et al., 2024).

Why do you get fewer reps close to your max?

The closer a weight gets to your max, the fewer reps you can do (Nuzzo et al., 2024). The reason is fatigue: it’s measured as a drop in your maximal strength, and an effort lighter than that strength can go on once fatigue has set in (Enoka and Duchateau, 2008). Put simply, with every rep your strength of the moment drops, and the set ends when it falls to the level of the weight.

You can see it in the bar: the more reps you string together in a set, the more it slows down, and in 18 trained men on the bench press or squat, that loss of speed went hand in hand with the rise in blood lactate, another marker of fatigue (Sánchez-Medina and González-Badillo, 2011). It’s a simplified picture: fatigue has many causes, which vary with the task (Enoka and Duchateau, 2008).

How many reps can you do at 80% of your max?

One analysis pooled 269 studies, 952 tests to failure and 7,289 people. At 80% of max, people did 8.8 reps on average on the bench press and 13.1 on the leg press; at 70%, 14.1 versus 19.0. In the general model, all exercises combined, that’s about 5 reps at 90% of max and 15 at 70% (Nuzzo et al., 2024).

Men or women, younger or older, beginners or trained: the analysis finds no clear difference. The only one that stands out is between the bench press and the leg press, and it’s clear only at light loads, up to about 50% of max; the authors still made a separate table for each of these two exercises. The data came mostly from people aged 20 to 40, in groups that were mostly male (66%) and trained (60%) (Nuzzo et al., 2024).

Why more reps for the legs? One lead: in 16 men, the squat allowed more reps than the bench press or the curl at the same share of max, especially at 60%, which the authors put down to the amount of muscle involved; the study looked at the squat, not the leg press (Shimano et al., 2006).

Do you have to attempt your max to know it?

No. 70 people, 34 men and 36 women aged 18 to 69, did sets of 1, 5, 10 and 20 rep maxes on the bench press and the leg press. Their max was best predicted from the 5-rep set, with a typical error of about 3 kg (7 lb) on the bench and 16 kg (35 lb) on the leg press; from 10 and then 20 reps, the prediction lost accuracy. The authors advise using no more than 10 reps in this kind of calculation (Reynolds et al., 2006).

The longer the set, the more people differ: at 80% of max, the standard deviation between people is about 2.5 reps, versus 4.4 at 60% (Nuzzo et al., 2024). A short, heavy set gives a better estimate of your max.

How do you estimate your max at your next session?

Take a heavy set, 10 reps at most. The studies above went to failure; if you stop before, count the reps you had left, to know how many you could have done to failure.

And do it for each exercise: at the same share of your max, you won’t necessarily do as many reps on the bench press as on the leg press (Nuzzo et al., 2024).