Free Tool
HubFit's free One Rep Max (1RM) Calculator accurately estimates your maximum lift using the Brzycki, Epley, and five other industry-leading formulas. Stop guessing your weights and get instant training percentages for strength and hypertrophy.
Knowing your One Rep Max (1RM) is widely considered the gold standard for measuring absolute strength. Whether you are a powerlifter, bodybuilder, or general fitness enthusiast, knowing the maximum weight you can lift for a single repetition helps you program your training effectively.
However, physically testing your 1RM can be dangerous and taxing on the Central Nervous System (CNS). This One Rep Max Calculator allows you to accurately estimate your maximum strength using mathematical formulas based on your sub-maximal lifts, without the risk of injury.
How to Use This Calculator
Our tool is designed to be versatile and precise. Here is how to get the best results:
Select Your Unit: Choose between Metric (kg) or Imperial (lbs).
Enter Weight Lifted: Input the weight you used for a specific exercise (e.g., Bench Press, Squat, Deadlift).
Enter Reps Performed: Input how many clean repetitions you completed. Note: For the most accurate results, use a weight where you can perform between 1 and 10 reps.
Choose Your Formula: By default, we use the Brzycki formula (the industry standard). However, you can select specific formulas like Epley or Wathan, or choose "Average" to calculate the mean result of all major scientific formulas.
Why Use a Calculator Instead of Testing?
Testing a true one-rep max requires a spotter, perfect form, and high physical readiness. If your form breaks down under maximal load, the risk of injury increases significantly.
Using a calculator offers three main benefits:
Safety: You can estimate your max by lifting a weight you can handle for 3–5 reps safely.
Programming: Most training programs ask you to lift a percentage of your 1RM (e.g., "3 sets of 8 at 70%"). This tool calculates those percentages for you instantly.
Progress Tracking: You can track your estimated strength gains week-over-week without needing to test a heavy single every session.
Understanding the Formulas
Unlike most calculators, this tool integrates the six most respected equations in exercise science.
1. Brzycki Formula
This is the most popular formula for general fitness. It is widely considered the most accurate for rep ranges between 1 and 10.
The Math:
Weight / (1.0278 - 0.0278 × Reps)
2. Epley Formula
Developed in 1985, the Epley formula is highly effective for compound movements like the squat. It tends to be slightly more accurate for higher rep ranges (10+ reps) compared to Brzycki.
The Math:
Weight × (1 + Reps/30)
3. Lombardi, Mayhew, O'Conner, and Wathan
These formulas offer slight variations based on different population data sets.
Mayhew and Wathan use exponential equations, which some coaches prefer for elite-level lifters.
O'Conner and Lombardi are simpler power functions often used in specific lifting communities.
The "Average" Feature
Not sure which formula to trust? Select the "Average (All Formulas)" option in the dropdown. Our tool runs your numbers through all six equations simultaneously and provides the mean value, giving you a balanced and highly probable 1RM estimate.
How to Use the Results for Training
Repetition Percentages
The "Repetition Percentages" tab is arguably the most useful feature for bodybuilders. If you know your 1RM is 100kg, but you want to do a set of 8 reps, look at the table to see exactly what weight you should put on the bar (approx. 78-80kg) to reach failure at that rep count.
Accuracy Disclaimer:
While these formulas are scientifically validated, they are estimates. Factors such as limb length, fast-twitch vs. slow-twitch muscle fiber dominance, and daily fatigue can influence your actual strength. Always use a spotter when attempting heavy lifts.
Training Percentages
Once you have your estimated 1RM, the most valuable information is how to apply it to your workouts. Look at the "Training Percentages" tab in the results section, which breaks down your strength zones.
Use these percentages to structure your programming, whether you are training for strength, hypertrophy (muscle growth), or endurance.
HubFit Overview
HubFit is the all-in-one coaching platform that makes it easy to build, scale, and automate your fitness business while staying fast and never feeling clunky. ⚡️
Watch our overview to see how it works.
