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Estimate your one-rep max from a set you lifted. This calculator does not give a number for every set: it gives one only where the Fitener app gives one, for compound lifts at 10 reps or fewer. For an isolation lift or a longer set it gives none, and says why.
Your set
Compound: several joints work together, as in squats, hinges, lunges, chest presses, overhead presses, pull-ups and pull-downs, and rows. With a barbell, dumbbells, a machine or a cable.
Isolation: one joint does the work, as in curls, triceps extensions, lateral raises, rear-delt raises, chest flyes, leg curls, glute isolation work, calf raises, and core work.
Estimated one-rep max
Estimated one-rep max from 100 kg × 5 reps, a compound lift.
The result is rounded to 0.1 kg, or to the nearest half pound in lb, as in the Fitener app. The estimate itself is coarser than that step: it is a floor, not a precise weight, for the reasons below.
Compound lift, 5 reps: yes. The Fitener app estimates a 1RM only for compound lifts at 10 reps or fewer.
100 kg × (1 + 5 ÷ 30) = 116.7 kg
Estimate, not a tested max. A floor, not a ceiling: if your set stopped short of failure, the real number is at least this.
How many reps you get at a given share of your max depends on the exercise and on you: machines allow more reps at the same percentage, small muscle groups fewer. On a machine or a small muscle group, read the number with that in mind.
The estimate works from how many reps you got with a weight. That link is tight for heavy sets of fewer than 10 reps and loosens as the reps go up: with more reps the estimate becomes less accurate, and it tends to come out too high. So the Fitener app stops at 10 reps, and this page stops there too. A set of 12 gets no number, not because it was a bad set, but because the number would be a poor one.
Three things decide whether a set gets an estimate:
That last point is why every number here is a floor, not a ceiling. The figure at the top means "at least this", not "exactly this". The only way to know your true one-rep max is to lift it.
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This page works it out once, from one set. In the Fitener app the same rule runs on every set you log: compound lifts at 10 reps or fewer get an estimate, next to the heaviest set you lifted. Log the same compound lift three times and its estimated 1RM trend appears.