Estimated 1RM and NSI: how to track strength without maxing out

Your one-rep max, or 1RM, is the heaviest weight you could lift for a single rep on a given exercise. It is the cleanest measure of raw strength, but actually testing it is fatiguing and carries more injury risk than a normal set, so few people do it often. An estimated 1RM solves that. It predicts your single from a set you already did, turning an everyday working set into a strength number without the load and recovery cost of a true max.

The logic is intuitive: the more reps you can complete with a given weight, the heavier your true single would be. Three reps at 200 pounds points to a higher max than ten reps at 135. A prediction formula puts a number on that relationship, so a set of 185 for 5 becomes an estimated max you can track set to set. When you do lift an actual single, that gets recorded as a true 1RM and kept separate from the estimate, so you never confuse a predicted number with a weight you really moved.

Estimated 1RM has been studied for decades, and a handful of named formulas are the standard. Each is a regression equation fit to population data, taking your weight (w) and reps (r) and returning a predicted single. Wellness Project defaults to the Lander formula and lets you switch to three others in Settings:

Lander(default): w × 100 / (101.3 − 2.67 × r)
Epley: w × (1 + r / 30)
Brzycki: w × 36 / (37 − r)
O’Conner: w × (1 + r / 40)

They all agree closely at low rep countsand drift apart as reps climb. Epley and O’Conner tend to read a little higher at high reps, Brzycki a little lower, and Lander sits in between. That spread is why accuracy is best at roughly five reps or fewer and gets looser past about ten, where one extra rep swings the estimate noticeably. The honest takeaway is that no formula is universally most accurate. Pick one and stay with it, because when you are tracking change over months, a consistent method matters far more than which equation you chose.

A 1RM on its own does not tell you whether you are strong. Two hundred and twenty-five pounds on the bench means something very different for a 150 pound lifter than for a 220 pound one, and the picture shifts again with age and sex. Strength normalization fixes that by scoring your lift against a standard built for a body like yours, so the number reflects relative strength rather than just absolute load.

That is what the Normalized Strength Index (NSI) does. It takes your best estimated 1RM on a movement, divides it by an intermediate-lifter standard for your bodyweight, age, and sex, and multiplies by 100. A score of 100 means you are exactly at the intermediate benchmark for that exercise. The bands run from below 75 (below average) through novice, average, intermediate, and advanced, up to 150 or higher (elite). For bodyweight movements like pull-ups, where there may be no loaded single to estimate from, the same idea is applied to your reps against a rep standard instead.

One thing to be clear about: NSI is an athletic comparison against population strength standards, not a health assessment. A low band is a starting point on a training journey, not a verdict on your wellbeing. The standards behind it come from published strength-science references, which you can read on our health sources page.