How to Use Our One Rep Max Calculator
To calculate your estimated 1RM, you only need to input data from a recent, challenging set. For the most accurate result, use a set where you performed between 2 and 10 repetitions to failure or near-failure.
Weight Lifted: Enter the total weight you lifted. Be sure to include the weight of the barbell itself (a standard Olympic barbell weighs 45 lbs or 20 kg). You can enter the weight in pounds (lbs) or kilograms (kg).
Reps Performed: Enter the total number of successful repetitions you completed with that weight.
Understanding Your Results
The primary number this calculator provides is your Estimated One-Rep Max (1RM). This is the predicted maximum weight you could lift for one single, clean repetition for a given exercise (like a squat, bench press, or deadlift).
How Is Your 1RM Calculated?
Your 1RM isn’t just a guess. It’s calculated using established predictive formulas developed by exercise scientists. The most common and reliable formulas are:
Our calculator processes your inputs using these tried-and-true methods to give you a reliable estimate of your maximal strength.
How to Use Your 1RM: The Training Percentage Chart
Your 1RM is more than just a number to brag about; it’s a tool to program your workouts. Training is typically based on percentages of your 1RM. Use the chart below to find the right weight for your workouts based on your goals.
This chart allows you to train with precision. If your program calls for a set of 5 reps, you know you should be using approximately 85% of your 1RM.
Frequently Asked Questions
How accurate is a 1RM calculator?
A 1RM calculator is surprisingly accurate for most lifters, especially when the input is based on a set of 10 reps or fewer. The formulas, like Brzycki and Epley, have been validated in scientific literature. However, accuracy can be influenced by your individual muscle fiber type (fast-twitch vs. slow-twitch), your neuromuscular efficiency, and the specific exercise. Think of the result as a very precise starting point, not an absolute certainty.
Which 1RM formula is the best one?
There is no single “best” formula for everyone. The Brzycki formula is often considered highly accurate for reps under 10. The Epley formula is also extremely popular and widely used in strength training apps and programs. Some other formulas (like Lombardi or O’Conner) may work better for different individuals or exercises. Our calculator uses a blend of the most reputable formulas to provide a balanced and reliable estimate.
How do I use my 1RM for muscle growth vs. strength?
You use your 1RM to select the right training intensity (% of 1RM) for your specific goal.
For Pure Strength: You’ll primarily train with heavier weights in lower rep ranges. This typically means working with 85% or more of your 1RM for sets of 1-6 reps.
For Muscle Growth (Hypertrophy): You’ll focus on moderate weight with higher volume. This typically means working with 70% to 85% of your 1RM for sets of 8-12 reps.
Concrete Example: Your bench press 1RM is 225 lbs.
How often should I test or calculate my 1RM?
You should only recalculate your 1RM when you see a clear sign of progress. A good rule of thumb is to re-evaluate every 4 to 8 weeks of consistent training. If you successfully complete your target reps and sets for a given weight and feel you could have done more, it’s a good time to use the calculator again with your new, higher numbers. Constantly testing your 1RM is unnecessary and can lead to overtraining.
Should I use this calculator for every exercise?
This calculator is most effective for major compound exercises like the squat, bench press, deadlift, and overhead press. It can be used for other accessory lifts (e.g., barbell rows, leg press), but it is generally less accurate and less useful for isolation exercises like bicep curls or leg extensions, where the concept of a true “one-rep max” is less relevant to training structure.
Why does my calculated 1RM feel heavier/lighter than I expected?
Several factors can cause a discrepancy.
Daily Readiness: Your strength on any given day is affected by sleep, nutrition, stress, and hydration. You may have calculated your 1RM on a “good” day and are now attempting it on a “bad” day, or vice versa.
Psychological Barrier: Lifting a weight you’ve never lifted before can be mentally intimidating, causing you to fail a lift you are physically capable of completing.
Specificity: Your strength is specific. If you calculated your 1RM based on a 10-rep set, your body is conditioned for that rep range. It might take a few sessions of training in a lower rep range (e.g., 3-5 reps) to “realize” the new strength potential the calculator predicted.
Now that you’ve determined your maximal strength, you can see how it stacks up. Use our Wilks Score Calculator to compare your strength to other lifters across different body weights. To make loading the bar easier, head over to our Barbell Plate Calculator to see exactly which plates to put on each side.
