The one-rep maximum—or 1RM for short—is the standard of measurement in strength training. Almost every training plan specifies weights as a percentage of this, and without this reference point, choosing weight plates comes down to a gut feeling. The catch: A true maximum attempt is exhausting, requires experience, and needs a spotter. This calculator takes the easier route and estimates your 1RM based on a normal working set—using six established formulas in direct comparison and a ready-made percentage table for your training plan.
Where the Formulas Come From
Behind every estimation formula lies the same observation: There is a fairly stable relationship between the weight you can lift for a certain number of repetitions and your maximum weight. If you can complete eight clean repetitions, you’re almost always at around 80 percent of your maximum. The formulas differ only in how they mathematically describe this relationship.
Epley (1985) uses a linear calculation: weight times (1 plus the number of reps) divided by 30. This is the most widely used variant and works well up to about ten reps.
Brzycki (1993) uses a fraction and yields slightly more conservative results than Epley at low repetition counts. For a single repetition, both formulas return exactly the input weight.
Lombardi uses a power function and estimates slightly lower in the mid-range. O’Conner’s method is the simplest and, accordingly, the coarsest. Wathen and Mayhew use exponential functions and are based on studies of the bench press—their estimates are usually the highest at high repetition counts.
Since no single formula is fundamentally more accurate than the others, the calculator displays the average of all six by default, along with the range. If the values are far apart, this is not an error but an honest measure of the uncertainty in your input.
How to Perform the Test Set Correctly
The estimate is only as good as the set you enter. Three factors determine this:
Close to muscle failure. The set must go as far as possible—to the point where you could have managed at most one more clean repetition. If you stop at eight even though twelve would have been possible, you’re underestimating your maximum by twenty percent or more.
Form over numbers. Only repetitions performed with proper form count. A half-squat with a rounded back isn’t a repetition—it’s an injury risk.
No more than eight to ten reps. The longer the set, the more strength endurance determines the result, and the less it reveals about your maximum strength. The most meaningful range is between three and six reps.
Make sure you’re well-warmed-up, well-rested, and ideally performing the first exercise of the session—a test set at the end of a long workout will consistently yield results that are too low.
Which exercises this applies to
The formulas are reliable for the major compound exercises with a barbell: squats, bench presses, deadlifts, shoulder presses, and bent-over rows. The relationship between repetitions and maximum strength has been best studied for these exercises.
It’s less useful for isolation exercises like bicep curls or lateral raises. In these exercises, many trainees manage a noticeably high number of repetitions with comparatively light weights, and the estimate ends up being too high. With deadlifts, it’s often the other way around: Because grip strength gives out first, the set ends before the legs and back have truly reached their limit.
The formulas generally work for machines as well, but the values aren’t comparable between different manufacturers—the leverage ratios and friction differ too much.
How to Use the Percentage Chart
The table converts your estimated maximum into specific working weights. As a rough rule of thumb: You train for maximum strength at 85 to 95 percent for one to five repetitions; for muscle building, at 70 to 85 percent for six to twelve repetitions; and anything below 65 percent primarily targets strength endurance.
Two practical tips. First: The rep counts in the table are averages. Some people can do twelve reps at 80 percent, others only six—this varies from person to person and doesn’t affect the accuracy of your 1RM. Second: When transferring the weight to the weight plates, round down. One kilo too little won’t cost you anything; one kilo too much can throw off your planned set.
The TDEE calculator shows how much energy strength training consumes overall and how to adjust your caloric needs accordingly. And the article on post-workout recovery explains why the rest periods between heavy workouts are at least as important as the workouts themselves.
For Gyms: The Test Set as a Coaching Tool
A true maximum effort test on the floor is neither necessary nor practical for most members. A guided test set with five to eight repetitions, on the other hand, takes two minutes, is safe, and provides the same basis for planning. Repeated every six to eight weeks, this creates a progress curve that motivates members because it shows development even when the scale doesn’t.
This is particularly worthwhile when coaching women: Getting started with strength training often fails due to misconceptions, not a lack of ability. We’ve compiled a list of these misconceptions in our article on strength training for women.
Frequently Asked Questions / FAQ
Which formula should I use?
When in doubt, use the average. If you need a single value that rarely disappoints in practice, use Epley for up to five repetitions and Brzycki for more than that. More important than the choice is that you stick with the same formula when comparing values over months.
Why is my actual maximum lower than that?
Because a true maximum attempt tests not only strength but also technique under maximum load, coordination, and mental fortitude. Those who rarely train with heavy weights often fall five to ten percent short of the calculated value during a test. With a few weeks of training in the 85 to 95 percent range, this gap usually closes.
Can I also calculate the 1RM for pull-ups or dips?
Yes, if you factor in your body weight. For pull-ups, add your body weight to the additional weight, run the formula, and then subtract your body weight again at the end. This gives you the additional weight for a single repetition.
How often should I actually go all out?
A true maximum attempt puts significant strain on tendons, ligaments, and the nervous system. Once or twice per training cycle is enough—so about every eight to twelve weeks. For everything in between, the estimated value is perfectly sufficient.
My value fluctuates from week to week—is that normal?
Yes. Sleep, nutritional status, stress, and previous training days can shift daily performance by as much as five percent. That’s why the trend over multiple measurements matters, not the single value.
Editorial Team, fitnessmarkt.de
Image source: #25743602 Drazen Zigic / freepik.com
Published on: 20 March 2026