Training tool

One-rep max calculator

Enter a recent hard set and get an estimated 1RM plus the load to use for 1 to 12 reps.

Weight lifted

Reps completed

Unit

kg lb

Want this done for you, every session?

FitJur logs every set you do, estimates your 1RM on each lift as you train, and shows how it moves week to week. No calculator needed.

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How the calculator works

Your one-rep max (1RM) is the most weight you can lift once with good form. Testing it is tiring and risky, so most programs estimate it from a set you can do for a few reps.

This calculator uses the Epley formula: weight times one plus reps divided by thirty. It is the most common estimate and the one FitJur uses on your logged sets, so the number here is the number you will see in the app. It is accurate up to about 6 reps and drifts high above 10.

Treat the number as a starting point. Your real max depends on the lift, the day, and how well you handle heavy singles. Adjust to what the bar actually does.

How many reps at each percentage

Most percentage-based programs, 5/3/1 included, write sets as a percentage of your 1RM. This chart turns any rep target into a weight, and it is where the loads in your results come from.

Reps	% of 1RM
1	97%
2	94%
3	91%
4	88%
5	86%
6	83%
7	81%
8	79%
9	77%
10	75%
11	73%
12	71%

Questions

How accurate is this?

Within a few percent for sets of 1 to 6 reps taken close to failure. Above 10 reps the estimate runs high, because how many reps you can do there depends more on endurance than strength.

How many reps should I use for the estimate?

Three to six reps taken close to failure gives the most reliable result. One or two reps is a near-direct test, and anything over ten depends more on endurance than strength.

Should I test my actual 1RM?

Only if your sport requires it or you are experienced and well rested. For most training, an estimated max is safer and just as useful for setting percentages.

What is a training max?

A training max is a deliberately lower number, usually 85 to 90 percent of your true or estimated 1RM, that percentage programs use so every prescribed set stays doable on a bad day.