One-Rep Max Calculator
Calculate your max for any lift with this 1RM calculator.
What is a One-Rep Max?
One-Rep Max (or 1RM) is short for “one-repetition maximum.”
One-rep max is a strength standard used by weightlifters, bodybuilders, and powerlifters to determine the maximum amount of weight they can lift in a single repetition for a given exercise.
Tracking and knowing your one-rep max using a 1-rep max calculator is helpful because it allows you to monitor your strength progress (why it auto-calculates in our Training Programs that come with FS Premium).
If you’re one-rep max is increasing, your strength training program is working, and you’re gaining muscle and strength.
How do I test my One-Rep Max?
The further away you are from 1 repetition, the less accurate the 1-Rep Calculator is.
And just loading as much weight as you think you can do for 1 rep on the bar isn’t an effective, useful, or safe idea.
You can make much more progress and get just as an accurate answer by testing you 3-6 Rep Max and re-entering that data into the calculator.
Follow this 7-step process to find your most accurate 1-Rep Max estimate:
Choose the exercise you want to test your 1RM on (in this example, squats)
Enter the last Weight X Reps you did into the 1RM calculator above (ex. 135lbs X 8 Reps for squats)
Note what 90% of your one-rep max with this information (ex. 90% calculates out to about ~150lbs.) You’re going to use this as your starting point to test your repetition max next.
Go through a 5-10 minute warm up in the next workout you have squats, then load the bar with 90% of your one-rep max (ex. ~150lbs.) Make sure this is the first exercise you’re doing that day to get the most accurate results.)
Do as many reps as you can with that weight (90% of your 1RM), ending just one rep shy of technical failure (the point at which your form begins to break down) if you don’t have a spotter, or take it to technical failure if you do have a spotter.
Go back to the 1-Rep Max Calculator above and enter the numbers from your most recent bench press workout.
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There are four common formulas to calculate One-Rep Max:
1. Brzycki formula: Weight × (36 / (37 – number of reps))
2. Epley formula: Weight × (1 + (0.0333 × number of reps))
3. Lombardi formula: Weight × (number of reps ^ 0.1)
4. O’Conner formula: Weight × (1 + (0.025 × number of reps))
We use the Brzycki's formula because it tends to be more accurate in the lower repetition range (around 10 reps and under). Like many 1RM formulas, its accuracy can decrease as the repetition number increases.
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The only real way to know how much weight you can lift for a single rep is to actually do it.
A single rep as heavy as you can go.
But that has a few drawbacks:
To really test your true 1RM, you would need at least several weeks of training with lighter weights and lower training volumes than normal.
Then, when you actually test your 1RM, you can’t be 100% confident the weight you’re putting on the bar is a weight you can actually complete (that’s why it’s called a test). And whenever you’re pushing too close to the edge, your form and technique likely break down and your risk of injury skyrocket.
And lastly, a true 1RM test is going to have you fatigued for at least several days after you test.
As you can see, simply testing your 1RM takes away weeks (if not months with an injury) from your actual programming. And your programming is what’s going to make you progress in the first place.
That’s why it’s generally better to test your 3-6 Rep Max that you can easily work into your regularly scheduled program.
