Use a recent, honest set
The estimate is only as good as the set behind it. Take your heaviest working set from the last week or two, the one where you had a rep or two left at most, and use those numbers.
One Rep Max Calculator
Enter the weight you lifted and the reps you got. We will estimate your one-rep max, then turn it into the percentages you actually train off.
Your estimated one-rep max
0kg
Based on 0 kg for 0 reps
Training percentages
What to load for a given percentage of your max.
| % of 1RM | Weight | Typical use |
|---|
Predicted rep maxes
Roughly what you should be able to hit for each rep target.
| Reps | Weight | % of 1RM |
|---|
These are estimates, not a tested max. The formula is only trusted to twelve reps, which is why longer sets are turned away, and a set taken close to failure gives a far better estimate than one with plenty left in the tank. Rating the effort helps: it tells the calculator how many reps you held back. Work up to a true max under a spotter, not off a calculator.
Making the number useful
An estimated max is a planning tool. Here is how to get something out of it.
Programme off percentages
Most strength work sits between 75 and 90 percent of your max, and most hypertrophy work below it. The table above turns your estimate into the actual weight for each band, so you are not doing arithmetic at the rack.
Recalculate as you progress
A max from two months ago will have you training too light. Recalculate whenever a working set moves, or log your sets in Korvi and let the app keep the number current for every lift on its own.
One rep max questions, answered
What people ask us most about estimating and training off a max.
What is a one-rep max?
Your one-rep max, or 1RM, is the heaviest weight you can lift for a single rep with good technique. It is the number most strength programmes are built around, because once you know it you can set every working set as a percentage of it rather than guessing what feels heavy on the day.
How accurate is a 1RM calculator?
Close enough to programme with, not close enough to put on a competition platform. An estimate from a set of three to six reps taken near failure usually lands within a few percent of a tested max. Past twelve reps it drifts far enough that we do not offer a number at all, because at that point you are measuring your work capacity as much as your strength.
How many reps should I use to estimate my max?
Between three and six, taken to within a rep or two of failure. Fewer reps than that and you are nearly testing a true max anyway. More than that and conditioning starts to decide the set. Use your heaviest honest set from a recent session rather than a number you once hit on a good day.
What does the effort rating do?
It tells the calculator how many reps you held back. RPE 10 means the set was everything you had; each point below that counts as one more rep you could have done, and those reps go into the estimate. A single at RPE 8 is treated as three effective reps, so it returns a higher max than the same single taken to failure would. Leave the slider unset and the set is treated as though you had nothing left. The scale starts at 6, because more than four reps in reserve tells us too little to estimate from: rate a harder set instead.
Should I test my one-rep max?
Most lifters do not need to. Testing a true max is taxing, needs a spotter and costs you training days either side of it. An estimate from your working sets tells you what to load next week, which is the thing you actually needed to know. Test when there is a reason to, such as a meet or the end of a training block.
How often does a one-rep max change?
For a newer lifter, meaningfully every few weeks. For someone more experienced, over months rather than weeks, and not evenly across lifts. That is the case for recalculating from recent sets rather than training off a figure from last spring, and it is why Korvi keeps the history for each exercise instead of a single stored number.
Does Korvi track this automatically?
Yes, and it uses this exact calculation. Log your sets in the Korvi app and your estimated max updates per exercise as you train, alongside your full history for that lift, so the number stays current without you coming back to a calculator. It is free on iPhone and Android, with no paywall and no card.
Stop recalculating it by hand
Korvi runs this same calculation on every set you log, and keeps your estimated max current for every exercise. Free on iPhone and Android.
