Enter the number of reps completed (1-30)
Enter weight and reps to calculate your 1RM
Heavy weight, low reps for maximum strength gains
Moderate weight and reps for muscle growth
Lighter weight, high reps for muscular endurance
How to Calculate Your One Rep Max
- 1
Enter your lift weight
Input the weight you lifted in pounds or kilograms. Switch between unit systems using the toggle at the top of the calculator. Use a weight you completed with proper form during a recent training session. - 2
Enter repetitions performed
Type the number of reps you completed at that weight. For best accuracy, use a set where you reached or came close to failure between 2 and 10 reps. Sets above 12 reps tend to produce less reliable estimates. - 3
Choose a formula
Select a prediction formula such as Brzycki, Epley, Lander, Lombardi, Mayhew, O'Conner, or Wathen. Each model was derived from different research populations. Brzycki is widely regarded as most accurate for sets under 10 reps. - 4
Review results and training zones
The calculator displays your estimated 1RM along with training weight recommendations at various percentages. Use the strength zone (85-95% of 1RM) for power work, the hypertrophy zone (65-80%) for muscle growth, and the endurance zone (50-65%) for conditioning.
Who Uses a One Rep Max Calculator?
Strength Athletes and Powerlifters
Personal Trainers and Coaches
Recreational Lifters Tracking Progress
Rehabilitation and Return-to-Sport
Why Calculate Your One Rep Max?
A one-rep max (1RM) is the heaviest weight you can lift for a single repetition with correct technique. It is the gold-standard measure of absolute strength and the foundation of percentage-based training programs used by powerlifters, Olympic weightlifters, and sports performance coaches worldwide. Rather than loading a barbell to failure, which carries real injury risk, this calculator lets you estimate your 1RM from a lighter set you have already completed safely. Enter your weight, your reps, and choose from seven peer-reviewed formulas to get an instant prediction plus a full breakdown of training zones.
Percentage-based programming depends on accurate 1RM values. When a coach writes "4 sets of 5 at 80%," the athlete needs a reliable max to translate that cue into actual plates on the bar. Under-estimating leads to wasted sessions; over-estimating leads to missed reps or injury. By cross-referencing formulas like Brzycki, Epley, and Wathen, you can triangulate a trustworthy number without ever grinding through a risky single. Pair your estimated max with the TDEE Calculator to align your calorie intake with your training intensity, or use the Macro Calculator to dial in protein targets that support strength gains.
Beyond the barbell, 1RM estimates are valuable for tracking long-term progress. Logging your estimated max for squat, bench press, and deadlift every training block gives you an objective trendline that bodyweight alone cannot provide. Combine this data with body composition metrics from the Body Fat Calculator or the BMI Calculator to get a complete picture of how your strength-to-weight ratio is evolving over time.
How It Compares
Several websites offer one-rep max calculators, but most provide only one or two formulas and no training-zone breakdown. Popular fitness apps like Strong and JEFIT include basic 1RM estimation, yet they lock percentage charts behind paid subscriptions. Dedicated strength-science sites such as Symmetric Strength provide solid estimates but require account creation to save results. This calculator gives you seven validated formulas, side-by-side comparison, and full training-zone recommendations with zero signup, no ads, and entirely client-side processing so your data never leaves your browser.
If you need a broader fitness assessment beyond raw strength numbers, the TDEE Calculator estimates daily calorie needs based on activity level, while the Water Intake Calculator helps you stay hydrated through heavy training sessions. For athletes cutting or bulking, the Macro Calculator translates calorie targets into precise protein, carbohydrate, and fat splits.