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One-Rep Max Calculator
Estimate your one-rep max from a recent lift using Epley, Brzycki, and Lombardi formulas, or enter a known 1RM directly to build a full training percentage chart.
Calculate your one-rep max
Choose whether to estimate from a recent lift, or enter a known 1RM directly.
Based on the average of Epley, Brzycki, and Lombardi.
Training percentage chart
Quick examples
How to use this one-rep max calculator
Choose your mode
Estimate from a recent lift, or enter a known 1RM directly.
Enter your lift details
Add the weight and reps, or your known one-rep max.
Choose a formula
Pick Epley, Brzycki, Lombardi, or the average of all three.
Check the chart
Use the percentage chart to plan training weights across rep ranges.
What is a one-rep max calculator?
A one-rep max calculator estimates the heaviest weight you could lift for a single repetition, based on a lighter set you already completed for multiple reps. Testing a true 1RM directly can be risky without a spotter and a full warm up, so most lifters and coaches rely on formula based estimates instead.
This tool also works in reverse, letting you enter a 1RM you already know and generating the same percentage based training chart without needing to recalculate anything from a recent lift.
One-rep max formulas explained
The Epley formula is one of the most widely used and tends to estimate slightly higher at higher rep counts.
The Brzycki formula is another common choice, generally considered reliable for rep ranges under about 10.
The Lombardi formula uses a different mathematical approach and can run higher than the other two, particularly at higher rep counts.
Why formulas disagree at higher reps
Each formula was built from a different dataset and a different mathematical relationship between reps and strength, so they naturally diverge as rep count rises. At 2 or 3 reps, the three formulas typically land within a few percent of each other. By 10 or 12 reps, the gap can widen to a meaningful amount of weight, which is why lower rep testing generally produces a more trustworthy estimate.
Averaging the three formulas, as this calculator offers as an option, does not guarantee a more accurate number, but it tends to smooth out the disagreement between individual formulas into a reasonable middle estimate.
Reading the training percentage chart
The percentage chart converts your estimated or known 1RM into working weights at common training percentages, from 50 percent up to 100 percent, along with a typical rep range associated with each percentage. This mirrors how many structured strength programs prescribe training loads, since percentages scale automatically as your strength improves over time.
The rep ranges shown next to each percentage are general estimates rather than fixed rules, since actual reps achievable at a given percentage vary by lifter, lift, and training experience.
Where this fits with your broader training plan
A 1RM estimate is most useful when it connects to the rest of your training and nutrition planning. If you train with dumbbells but a program is written around barbell percentages, the Dumbbell to Barbell Converter can help translate a percentage based target weight into an equivalent dumbbell load for lifts like the bench press or shoulder press.
If bodyweight training is part of your routine alongside barbell work, the Push-Up Weight Calculator estimates how much resistance different push up variations place on your upper body, which can help you compare intensity across very different types of exercises. And since building or maintaining strength depends heavily on nutrition, the Protein Intake Calculator can help you set a daily protein target that supports the training volume your percentage chart is built around.
For a broader strength benchmark beyond a single lift, the Farmers Carry by Age Calculator estimates a reasonable carry weight based on age, body weight, and training level, which is a useful cross check if you train grip and full body strength alongside your main barbell lifts.
Frequently asked questions
What is a one-rep max?
A one-rep max, usually shortened to 1RM, is the heaviest weight you can lift for a single complete repetition of an exercise with good form. Since actually testing a true 1RM can be risky without a spotter and a proper warm up, most lifters estimate it using a formula based on a lighter, safer set of multiple reps.
Which 1RM formula is most accurate?
No single formula is universally most accurate, since each one was derived from different populations and lift types. Epley and Brzycki tend to agree closely for rep ranges under about 10, while Lombardi can run noticeably higher at higher rep counts. Using the average of all three, as this calculator offers, often lands close to a reasonable middle estimate.
How many reps should I use to estimate my 1RM?
Formula based 1RM estimates are most reliable when calculated from a set of 10 reps or fewer. Beyond about 10 to 12 reps, fatigue and endurance start to play a larger role than raw strength, which makes every formula less accurate the higher the rep count goes.
How is the percentage chart used for training?
Many strength programs prescribe working weights as a percentage of your 1RM rather than an absolute number, since percentages scale naturally as your strength changes. For example, a program might call for 3 sets of 5 reps at 80 percent of your 1RM, and this chart converts that percentage directly into a weight based on your estimated max.
Should I actually test my true 1RM in the gym?
Testing a true 1RM can be useful for experienced lifters with a spotter, a proper warm up progression, and solid technique, but it is not necessary for most training goals and carries more injury risk than submaximal testing. Many coaches recommend estimating 1RM from a heavy but safer set instead, especially for beginners or for exercises without a spotter available.
Does this calculator work for any exercise?
The formulas were originally developed and validated mainly on barbell exercises such as the squat, bench press, and deadlift, where they tend to be reasonably reliable. Accuracy can vary more for isolation exercises, bodyweight movements, or lifts where technique breakdown happens well before true muscular failure.
Why do my estimated 1RM numbers change between formulas?
Each formula uses a slightly different mathematical relationship between reps and percentage of max, so they naturally diverge as rep count increases. At low rep counts, such as 2 or 3 reps, the formulas usually agree closely, while at higher rep counts the gap between them can widen to a meaningful amount of weight.
This tool is for educational purposes only. Always verify important results with a qualified professional.
