One Rep Max Calculator
Use the One Rep Max to track training progress. Enter your lifts, reps, or body stats to get personalised targets and performance benchmarks.
Calculator
Adjust values & calculateMost accurate with 1-10 reps
Percentage-Based Weights
Formula
The Brzycki formula estimates your one-rep max from a submaximal set. Epley uses: Weight × (1 + Reps/30). Lander uses: (100 × Weight) / (101.3 - 2.67123 × Reps). All formulas work best for sets of 1-10 reps.
Last reviewed: December 2025
Worked Examples
Example 1: Bench Press 1RM Estimate
Example 2: Squat Programming
Background & Theory
The One Rep Max (1rm) Calculator applies the following established principles and formulas. Fitness and nutrition science rests on well-characterized biochemistry and exercise physiology. Macronutrients provide the caloric substrate for all biological activity: protein yields 4 kilocalories per gram, carbohydrates yield 4 kilocalories per gram, and dietary fat yields 9 kilocalories per gram. These values, established by Wilbur Atwater in the early 1900s through bomb calorimetry, underpin all dietary energy calculations and macro-ratio planning for performance and body composition goals. One-repetition maximum, or 1RM, represents the highest load an individual can lift for a single complete repetition. The Epley formula estimates it as weight lifted multiplied by (1 + reps/30), while the Brzycki formula uses weight divided by (1.0278 − 0.0278 × reps). These formulas, validated across compound movements, allow athletes to program training intensity as a percentage of 1RM without maximal testing on every exercise. VO2 max, the maximum volume of oxygen consumed per kilogram of body weight per minute, is the gold standard measure of aerobic capacity and cardiovascular fitness. Field estimates use submaximal tests such as the Cooper 12-minute run, step tests, or resting heart rate-based equations. Higher VO2 max correlates strongly with reduced all-cause and cardiovascular mortality in population studies. Delayed onset muscle soreness is a normal inflammatory response to unaccustomed eccentric loading, peaking 24 to 72 hours after exercise. The physiological basis involves micro-trauma to myofibrils and subsequent prostaglandin-mediated inflammation. Progressive overload, the systematic increase of training volume or intensity over time, is the primary driver of skeletal muscle hypertrophy and strength adaptation, working through mechanotransduction pathways that upregulate mTOR signaling and protein synthesis. Protein synthesis requirements for muscle retention and growth, supported by research from the International Society of Sports Nutrition, typically range from 1.6 to 2.2 grams per kilogram of body weight per day for active individuals, with intake distributed across meals to optimize leucine-driven anabolic signaling.
History
The history behind the One Rep Max (1rm) Calculator traces back through the following developments. The formal pursuit of physical culture as a discipline dates to the late 19th century. Eugen Sandow, the German-born showman often called the father of modern bodybuilding, popularized structured resistance training and physique development in the 1890s, touring with live exhibitions and publishing training guides that influenced a generation of physical educators. His emphasis on measurement, proportionality, and exercise prescription introduced an empirical framework to strength training. The revival of the Olympic Games in Athens in 1896 by Pierre de Coubertin institutionalized competitive athletics globally and accelerated interest in sports science. Physical education programs expanded through the early 20th century in Europe and North America, and military fitness standards during both World Wars generated large datasets on human physical capacity. The American College of Sports Medicine, founded in 1954, was the first major scientific organization dedicated to exercise science, producing research guidelines on training prescription, physical fitness testing, and health-related fitness standards. ACSM's fitness testing protocols and exercise intensity guidelines remain foundational references today. Kenneth Cooper's 1968 book Aerobics introduced the concept of quantified aerobic fitness to popular audiences, coining the term and providing a points-based system for measuring and accumulating aerobic exercise. His 12-minute run test for VO2 max estimation became standard in fitness assessments worldwide and inspired the global aerobics fitness movement of the 1970s and 1980s. Sports nutrition as a formalized science emerged through the 1980s and 1990s, with the isolation of creatine's performance effects, the characterization of glycogen depletion and carbohydrate loading, and the first controlled trials on protein supplementation for strength athletes. The International Society of Sports Nutrition, founded in 2003, subsequently produced consensus position statements on protein, creatine, and other ergogenic aids grounded in systematic evidence reviews. The CrossFit movement, growing from the early 2000s, popularized functional fitness benchmarks and introduced structured intensity metrics to everyday gym culture.
Key Features
- Estimate one-rep max from a submaximal lift using the Epley and Brzycki formulas, and generate percentage-based training loads for common strength programming schemes.
- Calculate personalized heart rate training zones using the Karvonen method with heart rate reserve, requiring only resting heart rate and age-predicted maximum to define five intensity zones.
- Estimate VO2 max from common field tests including the 1.5-mile run, the Cooper 12-minute run, and the Rockport walking test, providing a cardiorespiratory fitness classification.
- Predict running finish time for standard race distances based on a recent training pace, and convert between pace per mile, pace per kilometer, and average speed.
- Calculate calories burned during specific exercises by type, body weight, and duration using MET values, giving a practical estimate for logging or planning energy balance.
- Plan progressive overload across a training cycle by automatically incrementing weekly volume or load according to user-defined progression rates and deload frequency.
- Design HIIT sessions by specifying work-to-rest ratio, interval duration, and total workout time, with output showing rep count, total work time, and estimated calorie expenditure.
- Estimate cumulative training load using session RPE multiplied by duration, and flag when weekly load increases exceed safe thresholds to help manage injury risk and recovery needs.
Frequently Asked Questions
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy
One Rep Max Calculator Formula
Brzycki: 1RM = Weight × (36 / (37 - Reps))
The Brzycki formula estimates your one-rep max from a submaximal set. Epley uses: Weight × (1 + Reps/30). Lander uses: (100 × Weight) / (101.3 - 2.67123 × Reps). All formulas work best for sets of 1-10 reps.
One Rep Max Calculator — Worked Examples
Example 1: Bench Press 1RM Estimate
Problem: You bench pressed 225 lbs for 5 reps. What is your estimated 1RM?
Solution: Using Brzycki: 1RM = 225 × (36 / (37 - 5)) = 225 × 1.125 = 253 lbs\nTraining Max (90%): 253 × 0.90 = 228 lbs\n85% working weight: 253 × 0.85 = 215 lbs (3-4 reps)\n75% working weight: 253 × 0.75 = 190 lbs (6-8 reps)
Result: Estimated 1RM: 253 lbs | Training Max: 228 lbs
Example 2: Squat Programming
Problem: You squatted 315 lbs for 3 reps. What weights should you use for a 5/3/1 program?
Solution: Using Brzycki: 1RM = 315 × (36 / (37 - 3)) = 315 × 1.059 = 334 lbs\nTraining Max (90%): 334 × 0.90 = 300 lbs\nWeek 1 (5s): 65% = 195, 75% = 225, 85% = 255\nWeek 2 (3s): 70% = 210, 80% = 240, 90% = 270\nWeek 3 (1s): 75% = 225, 85% = 255, 95% = 285
Result: Estimated 1RM: 334 lbs | Training Max: 300 lbs
One Rep Max Calculator — Frequently Asked Questions
What is a one-rep max (1RM)?
A one-rep max is the maximum amount of weight you can lift for a single repetition with proper form. It's the gold standard for measuring absolute strength and is used to program training percentages. Rather than actually testing a true 1RM (which carries injury risk), most lifters estimate it using formulas based on submaximal sets. For example, if you can bench press 225 lbs for 5 reps, your estimated 1RM is approximately 253 lbs using the Brzycki formula.
What is a training max and why use 90%?
A training max is typically set at 90% of your estimated 1RM. Programs like 5/3/1 by Jim Wendler use the training max instead of your true max to calculate working weights. This provides a built-in buffer that ensures you can complete all prescribed reps with good form, allows room for progression over multiple cycles, and accounts for day-to-day strength fluctuations. Starting lighter and building up leads to more sustainable long-term strength gains.
How do I calculate my one-rep max for weightlifting?
The Epley formula estimates 1RM: weight x (1 + reps/30). For example, if you bench press 150 lbs for 8 reps, your estimated 1RM is 150 x (1 + 8/30) = 190 lbs. Use this for programming percentages without the risk of actual max attempts.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.
How do I verify One Rep Max Calculator's result independently?
The Formula section on this page shows the equation used. You can reproduce the calculation manually or in a spreadsheet using those steps. Compare your answer against the worked examples in the Examples section, which use known reference values so you can confirm the calculator is behaving as expected.