Skip to main content
hubfit
Start for free
Free Tool

One Rep Max Calculator

Estimate your 1RM for any lift. Choose from six scientific formulas (Brzycki, Epley, Mayhew, O'Conner, Lombardi, and Wathan) or average them all for the most reliable estimate.

Your lift

Unit
Most accurate at 1–10 reps. Maximum 15 reps.
Industry standard, most accurate for 1–10 reps

Enter your weight and reps to see your estimated 1RM, percentage table, and training zones.

Track PRs automatically for every client

HubFit logs max weight, max volume, and estimated 1RM on every session. Clients see PR badges the moment they hit a new record.

Explore HubFit →

What is a One Rep Max (1RM)?

Your One Rep Max is the maximum weight you can lift for a single repetition with proper form. It is widely considered the gold standard for measuring absolute strength, whether you are a powerlifter, bodybuilder, or general fitness enthusiast. Knowing your 1RM helps you programme your training effectively, since most strength and hypertrophy programmes express loading as a percentage of your 1RM (e.g. “3 sets of 5 at 85%”). However, physically testing your true 1RM can be dangerous and taxing on the Central Nervous System (CNS). This calculator lets you accurately estimate your maximum strength from sub-maximal lifts.

How to Use This Calculator

Select your unit (Metric or Imperial), enter the weight you lifted for a specific exercise (e.g. Bench Press, Squat, Deadlift), and input how many clean repetitions you completed. For the most accurate results, use a weight where you can perform between 1 and 10 reps. By default, the calculator uses the Brzycki formula (the industry standard), but you can select Epley, Mayhew, O'Conner, Lombardi, or Wathan, or choose “Average” to calculate the mean of all six formulas simultaneously.

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 key advantages:

  • Safety. Estimate your max by lifting a weight you can handle for 3–5 reps safely. No failed lifts, no spotter required.

  • Programming. Most training programmes ask you to lift a percentage of your 1RM. This tool calculates those percentages and exact weights instantly.

  • Progress Tracking. Track estimated strength gains week-over-week without needing to attempt a heavy single every session.

Understanding the Formulas

Unlike most calculators, this tool integrates the six most respected equations in exercise science. Not sure which formula to trust? Select the “Average (All Formulas)” option to run your numbers through all six equations simultaneously and get the mean value, a balanced and highly probable 1RM estimate.

Brzyckiw ÷ (1.0278 − 0.0278 × r)The most popular formula for general fitness. Widely considered the most accurate for rep ranges between 1 and 10.
Epleyw × (1 + r / 30)Developed in 1985. Highly effective for compound movements like the squat. Slightly more accurate for higher rep ranges (10+ reps).
Mayhew(100w) ÷ (52.2 + 41.9e^(−0.055r))Exponential equation preferred by some coaches for elite-level lifters.
Wathan(100w) ÷ (48.8 + 53.8e^(−0.075r))Exponential equation preferred by some coaches for elite-level lifters.
O’Connerw × (1 + 0.025 × r)Simpler power function used in specific lifting communities.
Lombardiw × r^0.10Simpler power function used in specific lifting communities.

How to Use the Results for Training

The Repetition Percentages tab is arguably the most useful feature for bodybuilders. If you know your 1RM is 100 kg, 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. 78–80 kg) to reach failure at that rep count.

Once you have your estimated 1RM, the most valuable information is how to apply it to your workouts. The Training Zones tab breaks down your strength zones. Use these percentages to structure your programming, whether you are training for strength, hypertrophy (muscle growth), or endurance.

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.

Frequently asked questions.

A One Rep Max (1RM) is the maximum amount of weight an individual can lift for a single, complete repetition of a specific exercise (like the squat, bench press, or deadlift) with proper form. It is the purest measure of absolute muscular strength.
You calculate your 1RM using a mathematical formula based on a sub-maximal lift. You perform an exercise for 2 to 10 repetitions until failure, and the calculator uses your weight and rep count to estimate your maximum potential strength using established formulas like Brzycki or Epley.
The Brzycki and Epley formulas are generally considered the most accurate and reliable for estimating 1RM across different populations. The Brzycki formula tends to be favored for lower rep counts (2–6 reps), while the Epley formula is often more accurate for higher rep counts (7–10+ reps).
A calculated 1RM is an estimation, while a tested 1RM is a true measure. A calculated 1RM is highly accurate (often within 3–5%) but cannot account for your central nervous system (CNS) readiness or peak motivation on a given day. Always test your maximum in a gym with caution.
For the highest accuracy, you should enter a weight you can lift for 2 to 10 repetitions. Calculations based on sets of 15 or more reps tend to be less accurate due to the increased influence of muscular endurance.
Your 1RM is the maximum weight (e.g., 100 kg). The Rep Max Percentage (or Training Percentage) is the specific percentage of your 1RM you should lift to achieve a certain number of repetitions (e.g., 85% of your 1RM is the estimated weight you can lift for 5 reps).
For hypertrophy (muscle growth), you should typically train using weights that fall between 65% and 85% of your 1RM. This corresponds to the 6–12 repetition range, maximizing volume and time under tension.
To maximize absolute strength, training should focus on weights between 85% and 100% of your 1RM. This typically involves sets of 1 to 5 repetitions and requires longer rest periods.
Yes, the 1RM calculator can be used for any resistance exercise, including dumbbell presses, barbell rows, and leg extensions. Just ensure the weight and rep count are based on a challenging, sub-maximal set.
It is most critical to calculate your 1RM for the major compound lifts (Squat, Bench Press, Deadlift, Overhead Press) as these form the foundation of most strength programs. You only need to re-calculate when you want to track progress or adjust your training phase.
Most coaches recommend recalculating every 4–8 weeks or at the start of a new training block. Frequent retesting isn't necessary. Track your estimated 1RM based on rep PRs and adjust programming accordingly.
The common 1RM prediction formulas (like Brzycki and Epley) are gender-neutral, relying only on the relationship between weight and repetitions, not demographic data.

More free tools

BMR & TDEE Calculator

Calculate your Basal Metabolic Rate and total daily calorie needs by activity level.

Use tool →

Body Fat Calculator

Estimate body fat percentage using the U.S. Navy tape test method.

Use tool →

Instagram Bio Generator

Generate 24 Instagram bio variations for your fitness coaching business.

Use tool →

Supercharge your coaching business

See why HubFit is the coaching platform of choice for modern fitness professionals.

Start for freeSee our plans