Last updated:
One Rep Max Calculator
Estimate one-rep max using Epley, Brzycki, Lander, and Lombardi formulas with training load percentages.
One Rep Max Calculator
Free one rep max (1RM) calculator — estimate your max lift using Epley, Brzycki, Lander, or Lombardi formulas with AI-powered training insights.
Enter values above to see results.
About This Calculator
Related Articles
📚 Learn More
Explore our in-depth guides related to this calculator
The Complete BMI Guide 2026: Formula, Charts, Healthy Ranges & Alternatives
The definitive 2026 BMI guide: metric and imperial formulas with worked examples, WHO/CDC adult categories, Asian-adjusted thresholds, children's BMI percentile charts, athlete limitations, disease risk associations, waist-to-height ratio, body fat percentage alternatives, and 10 evidence-based strategies to reach a healthy weight. Includes free BMI, calorie, and body fat calculators.
The 2026 Evidence-Based Weight Loss Guide: Calorie Deficit, TDEE, Macros, GLP-1 Era & The Science of Sustainable Fat Loss
The most comprehensive 2026 weight-loss guide: calorie deficit math (500 kcal/day = 1 lb/week), TDEE & BMR formulas (Mifflin-St Jeor, Katch-McArdle), 0.7–1.0 g/lb protein for muscle retention, NEAT and adaptive thermogenesis, diet breaks, refeeds, the GLP-1 / semaglutide / tirzepatide era, body recomposition vs cutting, and free CDC-aligned calorie deficit, TDEE, BMR, and body fat calculators.
Calories & Nutrition 2026: The Complete Science-Based Guide to TDEE, Macros & Every Goal
Comprehensive 2026 guide covering calories, TDEE, BMR, macros, calorie deficit for fat loss, surplus for muscle gain, protein targets, micronutrients, meal timing, food labels, hidden calories and the 10 most common tracking mistakes. 25+ worked examples, USDA & WHO references.
A one-rep max (1RM) is the maximum weight lifted for a single repetition. The Epley formula estimates 1RM = weight × (1 + reps / 30); Brzycki: 1RM = weight × 36 / (37 − reps). Most accurate for 3–8 rep sets. Training zones: Strength 85–95% 1RM (1–5 reps);Hypertrophy 65–85% (6–15 reps);Endurance 50–65% (15+ reps). Avoid true 1RM testing without a spotter; submaximal estimation via 3–5 rep sets is safer for most lifters.
🏋️ One-Rep Max — Complete Guide
Reviewed by CalculatorApp.me Health Editorial Team · Updated June 2026 · 10 min read
How 1RM Is Calculated
Your one-repetition maximum (1RM) is the heaviest weight you can lift for a single complete repetition with proper form. It is the universal reference point for strength training intensity prescription.
Rather than performing a risky true 1RM test, submaximal prediction formulas estimate 1RM from a multi-rep set. The Epley formula (1985) is the most widely used: 1RM = weight × (1 + reps/30).
Formulas are most accurate for 3–8 repetitions. Above 10 reps, prediction error increases significantly (±10–15%) because muscular endurance contributes more relative to maximum strength. For best accuracy, use 3–5 rep sets at 85–90% perceived effort.
Training Intensity Zones
- ▸95–100% 1RM → Max strength (1 rep)
- ▸90–95% → Near-max (1–2 reps)
- ▸85–90% → Strength (2–4 reps)
- ▸75–85% → Strength-hypertrophy (5–8 reps)
- ▸65–75% → Hypertrophy (8–15 reps)
- ▸55–65% → Muscular endurance (15+ reps)
- ▸<55% → Active recovery / technique work
- ▸Powerlifting meets: 90–103% of max
1RM Formula Comparison
| Formula | Equation | Best For | Accuracy |
|---|---|---|---|
| Epley (1985) | w × (1 + r/30) | General use, most widely validated | Best for 1–10 reps |
| Brzycki (1993) | w × 36 / (37 − r) | Lower rep ranges (1–10) | Very accurate for 1–8 reps |
| Mayhew (1992) | w × 100 / (52.2 + 41.9 × e^(−0.055r)) | Research/lab settings | Moderate; works for 3–12 reps |
| O'Conner (1989) | w × (1 + 0.025r) | Quick estimates only | Less accurate for >8 reps |
| Lombardi (1989) | w × r^0.1 | Varies by lift type | Less commonly used |
| Wathan (1994) | w × 100 / (48.8 + 53.8 × e^(−0.075r)) | Comparable to Mayhew | Validated on multiple lifts |
All formulas produce within 5–10% of each other for 3–8 rep sets. Beyond 10 reps, divergence increases substantially.
One-Rep Max Myths vs Facts
Frequently Asked Questions
How often should I test my 1RM?›
Most trained athletes test 1RM at the end of a training block (every 8–16 weeks). Testing more frequently interrupts training and risks overuse injury. Powerlifters peak for competition-specific attempts 2–4 times per year.
What is the Epley formula?›
Epley (1985): 1RM = weight × (1 + reps/30). For example, 10 reps at 100 kg: 1RM ≈ 100 × (1 + 10/30) = 133 kg. It is the most widely validated and used formula in strength training research and practice.
How do I use 1RM percentages in programming?›
Multiply your estimated 1RM by the desired percentage. E.g., for hypertrophy at 75% 1RM with an estimated 100 kg max: use 75 kg for working sets. Adjust week-to-week using progressive overload — add 2.5–5% when you complete all reps with good form.
Is the 1RM calculator accurate for all exercises?›
It's most accurate for barbell compound lifts (squat, bench press, deadlift, overhead press). For machine exercises, cable movements, and bodyweight exercises, results are less reliable due to different muscle fiber recruitment patterns and range of motion.
What is an RPE scale and how does it relate to 1RM?›
RPE (Rate of Perceived Exertion) 10 = absolute maximum (1RM). RPE 9 = 1 rep left in the tank; RPE 8 = 2 reps left. Modern powerlifting uses RPE to autoregulate training load rather than rigid percentages, as daily performance varies with sleep, nutrition, and recovery.
Is it safe to do a true 1RM test?›
With a competent spotter (for bench press), proper equipment (power rack with safeties), and a proper warm-up, true 1RM testing is safe for experienced lifters. Beginners and those with injury history should use submaximal prediction only. Avoid true 1RM testing when fatigued or sick.
What does "relative strength" mean?›
Relative strength is 1RM divided by bodyweight (kg/kg or lb/lb). For example, a 70 kg person squatting 140 kg has a relative strength of 2.0×. Relative strength standardizes comparisons across different body sizes and is the basis for weight class competition in powerlifting.
How do powerlifting strength standards compare?›
Beginner bench press: 1.0× bodyweight (male). Intermediate: 1.25×. Advanced: 1.5×. Elite: 2.0×. Female standards are approximately 60–65% of male absolute values. Standards vary by federation and weight class.
References & Further Reading
- • Epley B — Poundage Chart, Body by Science (Boyd Epley Workout, 1985)
- • Brzycki M — Strength testing — predicting a one-rep max from reps-to-fatigue, JOPERD 1993;64(1):88-90
- • NSCA — Essentials of Strength Training and Conditioning, 4th Ed. (Haff & Triplett, 2016)
- • Reynolds JM et al. — Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry, J Strength Cond Res 2006;20(3):584-92
Related Calculators
Explore All Health & Fitness Calculators
Strength, cardio, nutrition, and body composition tools — all free.
Reviewed by CalculatorApp.me Health Team
One Rep Max (1RM) Calculator — Complete Guide
Epley, Brzycki, and Lombardi formulas, rep-percentage charts, progressive overload, periodization models, and strength standards.
1RM
Maximum single lift
~85%
5-rep max percentage
2-3 min
Rest for strength sets
1-2%/wk
Progressive overload rate
What Is One Rep Max (1RM)?
The one-repetition maximum (1RM) is the maximum weight a person can lift for a single repetition with proper form. It is the gold standard for measuring absolute muscular strength and is used to prescribe training loads as percentages (e.g., "work at 75% of your 1RM"). Knowing your 1RM allows precise programming for hypertrophy, strength, power, or endurance goals.
Rather than testing a true 1RM (which carries injury risk and requires maximal effort), most athletes estimate it from a submaximal set — lifting a lighter weight for multiple reps and applying a prediction formula. Research shows that sets of 3-10 reps provide the most accurate predictions; sets above 12 reps progressively underestimate true 1RM because endurance factors begin to dominate.
The 1RM is exercise-specific and muscle-group-specific — your squat 1RM says nothing about your bench press 1RM. Ratios between lifts (e.g., squat should be ~1.2-1.5× bench) can reveal imbalances and guide programming priorities.
1RM Estimation Formulas
1RM = w × (1 + r/30) Where: w = weight lifted r = number of repetitions Example: 225 lbs × 5 reps 1RM = 225 × (1 + 5/30) 1RM = 225 × 1.1667 1RM = 262.5 lbs Percentage calculation: %1RM = 1 / (1 + r/30) × 100 Rep → %1RM mapping: 1 rep = 100% (actual max) 3 reps = 90.9% 5 reps = 85.7% 8 reps = 78.9% 10 reps = 75.0% 12 reps = 71.4% 15 reps = 66.7% 20 reps = 60.0%
Published by Boyd Epley (1985). The most widely used formula due to simplicity. Slightly overestimates for very low reps and underestimates for very high reps.
1RM = w × (36 / (37 − r)) Equivalently: 1RM = w / (1.0278 − 0.0278 × r) Example: 225 lbs × 5 reps 1RM = 225 × (36/(37−5)) 1RM = 225 × (36/32) 1RM = 225 × 1.125 1RM = 253.1 lbs %1RM from reps: %1RM = (37 − r) / 36 × 100 Rep → %1RM: 1 rep = 100% 3 reps = 94.4% 5 reps = 88.9% 8 reps = 80.6% 10 reps = 75.0% 12 reps = 69.4% 15 reps = 61.1% Note: Becomes undefined at 37 reps (mathematical limit of the formula)
Published by Matt Brzycki (1993). Tends to produce more conservative estimates than Epley. Particularly accurate for sets of 1-10 reps.
Lombardi (1989):
1RM = w × r^0.10
O'Conner et al. (1989):
1RM = w × (1 + 0.025 × r)
Mayhew et al. (1992):
1RM = w / (0.522 + 0.419 × e^(−0.055 × r))
Example: 225 lbs × 5 reps:
Lombardi:
= 225 × 5^0.10
= 225 × 1.175
= 264.3 lbs
O'Conner:
= 225 × (1 + 0.025 × 5)
= 225 × 1.125
= 253.1 lbs
Mayhew:
= 225 / (0.522 + 0.419 × e^−0.275)
= 225 / 0.840
= 267.8 lbsMultiple formulas exist because 1RM prediction depends on training status, muscle fiber type, and exercise type. Averaging 2-3 formulas improves accuracy.
Comparison at 225 lbs × 5 reps: Epley: 262.5 lbs Brzycki: 253.1 lbs Lombardi: 264.3 lbs O'Conner: 253.1 lbs Mayhew: 267.8 lbs Average: 260.2 lbs Accuracy factors: • Rep range: 1-5 reps most accurate • Training level: Trained > untrained • Exercise: Compound > isolation • Muscle groups: Legs > chest > arms Best practices: 1. Test with 3-5 reps for accuracy 2. Use the same formula consistently 3. Average 2-3 formulas for planning 4. Actual 1RM testing trumps formulas 5. Retest every 4-8 weeks of training Real-world accuracy: ±5% for 3-5 reps (well-trained) ±10% for 8-12 reps ±15%+ for 15+ reps
Research by LeSuer et al. (1997) found that no single formula is superior for all exercises. Brzycki and Epley are most widely validated.
Rep-Percentage Chart & Training Zones
| Reps | % 1RM (Epley) | % 1RM (Brzycki) | Training Goal | Sets | Rest Period |
|---|---|---|---|---|---|
| 1 | 100% | 100% | Maximal Strength | 1-3 | 3-5 min |
| 2 | 93.5% | 94.4% | Strength / Power | 3-5 | 3-5 min |
| 3 | 90.9% | 91.7% | Strength | 3-5 | 3-5 min |
| 4 | 88.2% | 88.9% | Strength | 3-5 | 2-4 min |
| 5 | 85.7% | 86.1% | Strength | 3-5 | 2-4 min |
| 6 | 83.3% | 83.3% | Strength-Hypertrophy | 3-4 | 2-3 min |
| 8 | 78.9% | 77.8% | Hypertrophy | 3-5 | 1.5-2 min |
| 10 | 75.0% | 72.2% | Hypertrophy | 3-4 | 1-2 min |
| 12 | 71.4% | 66.7% | Hypertrophy-Endurance | 2-3 | 60-90 sec |
| 15 | 66.7% | 61.1% | Muscular Endurance | 2-3 | 30-60 sec |
| 20 | 60.0% | 52.8% | Endurance | 2-3 | 30-60 sec |
Strength Standards (Body-Weight Ratios)
| Lift | Beginner | Novice | Intermediate | Advanced | Elite |
|---|---|---|---|---|---|
| Back Squat (M) | 0.75×BW | 1.25×BW | 1.75×BW | 2.5×BW | 3.0×BW |
| Back Squat (F) | 0.50×BW | 0.75×BW | 1.25×BW | 1.75×BW | 2.25×BW |
| Bench Press (M) | 0.50×BW | 1.0×BW | 1.5×BW | 2.0×BW | 2.5×BW |
| Bench Press (F) | 0.35×BW | 0.65×BW | 1.0×BW | 1.5×BW | 1.75×BW |
| Deadlift (M) | 1.0×BW | 1.5×BW | 2.0×BW | 2.75×BW | 3.5×BW |
| Deadlift (F) | 0.65×BW | 1.0×BW | 1.5×BW | 2.25×BW | 2.75×BW |
| OHP (M) | 0.35×BW | 0.65×BW | 1.0×BW | 1.35×BW | 1.65×BW |
| OHP (F) | 0.25×BW | 0.45×BW | 0.65×BW | 0.90×BW | 1.15×BW |
BW = body weight. Standards based on Symmetric Strength and ExRx.net data for healthy adults. M = Male, F = Female, OHP = Overhead Press.
History of Strength Testing & Training
Milo of Croton — Progressive Overload Origin
The legendary Greek wrestler Milo reportedly carried a growing calf daily until it became a bull — the earliest description of progressive overload. While likely embellished, the principle (gradually increasing load) remains the most fundamental concept in strength training.
DeLorme — Modern Resistance Training
US Army physician Thomas DeLorme published his progressive resistance exercise protocol for rehabilitating injured soldiers. He established the concept of training with percentages of maximum capacity and prescribed 3 sets of 10 repetitions — a structure (3×10) that remains the most common gym prescription today.
Epley Formula Published
Boyd Epley, strength coach at the University of Nebraska, published his 1RM prediction formula: 1RM = w × (1 + r/30). Its simplicity made it the most widely adopted formula. It allowed coaches to prescribe training loads from submaximal tests, reducing injury risk from maximal testing.
Brzycki Alternative Formula
Matt Brzycki proposed the formula 1RM = w × 36/(37−r), which produces more conservative estimates at higher rep ranges. Research comparing formulas found Brzycki slightly more accurate for bench press, while Epley better predicted squat and deadlift 1RM.
Prilepin's Chart Gains Mainstream Adoption
Soviet weightlifting coach Alexander Prilepin's research on optimal training volumes (number of reps at each intensity) was widely disseminated. His chart prescribes 1-3 reps at 90%+ 1RM (4-10 total reps), 3-6 reps at 80-89% (10-20 total), and 3-6 reps at 70-79% (12-24 total).
Meta-Analysis Validates Volume-Matched Training
Schoenfeld et al. published a meta-analysis showing that both heavy (85%+ 1RM) and moderate (60-80% 1RM) loads produce similar hypertrophy when volume is equated — but heavy loads are superior for maximal strength gains. This validated the use of moderate loads for muscle growth.
Key Research & Data
Schoenfeld et al. — JSCR (2017)
Strength vs. Hypertrophy Rep Ranges
Meta-analysis of 21 studies: loads ≥60% 1RM produced equivalent hypertrophy to loads ≥85% 1RM when volume was equated. However, heavier loads (85%+) were significantly superior for 1RM strength gains. This supports using the 1-5 rep range for strength and 6-12+ for hypertrophy.
LeSuer et al. — JSCR (1997)
Accuracy of 1RM Prediction Equations
Compared Epley, Brzycki, Mayhew, O'Conner, and Lombardi formulas against actual 1RM in bench press, squat, and deadlift. All formulas were most accurate with 3-5 reps (±5-7%). Accuracy decreased above 10 reps. No single formula was universally superior — averaging multiple formulas improved accuracy.
Grgic et al. — Sports Med (2020)
Effects of Rest Intervals on Strength
Systematic review: rest periods of 3-5 minutes between sets produced greater strength gains than 1-2 minutes. For hypertrophy, shorter rest (60-90 seconds) was equally effective due to greater metabolic stress. For 1RM testing, 3-5 minutes between attempts is recommended.
Peterson et al. — MSSE (2005)
Dose-Response for Strength Training
Meta-analysis of 177 studies: trained athletes need higher intensities (85%+ 1RM) for maximal strength gains than untrained individuals (60% 1RM sufficient). Frequency of 2×/week per muscle group was superior to 1× or 3×. Periodization models significantly outperformed constant loading.
Strength Training Myths vs. Facts
You must train heavy (1-3 reps) to build muscle.
Hypertrophy occurs across a wide rep range (6-30+ reps) as long as sets are taken close to failure. Research shows similar muscle growth at 30% vs 85% 1RM when volume is equated. However, heavy training (85%+) IS superior for maximal strength (1RM) gains.
Testing your 1RM is dangerous and unnecessary.
While maximal testing carries higher injury risk than submaximal training, proper preparation (warm-up, progressive loading, spotters) makes it safe. However, 1RM estimation formulas make direct testing unnecessary for most trainees. True 1RM testing is mainly needed for competitive powerlifters.
You should always train to failure for maximum gains.
Training to failure is not required for strength or hypertrophy gains — leaving 1-3 reps in reserve (RPE 7-9) produces similar results with better recovery. Consistently training to failure increases CNS fatigue, extends recovery time, and may increase injury risk. Reserve failure for isolation exercises and deload periods.
Women get 'bulky' from heavy lifting.
Women produce ~15-20× less testosterone than men, making excessive muscle gain virtually impossible. Heavy lifting increases strength, bone density, and muscle tone without dramatic size increases. Most female strength athletes train heavy and maintain lean, athletic physiques.
Frequently Asked Questions
How do I safely test my 1RM?▼
Which formula should I use?▼
How often should I retest my 1RM?▼
What percentage should I use for building muscle?▼
What is progressive overload?▼
Why doesn't my 1RM match the calculator?▼
What is RPE and how does it relate to 1RM?▼
Is my squat-to-bench ratio important?▼
Can I estimate 1RM from a 20-rep set?▼
What is the difference between absolute and relative strength?▼
How does age affect 1RM?▼
What is periodization?▼
References
- Epley, B. — Poundage Chart (University of Nebraska, 1985)
- LeSuer et al. — Accuracy of Prediction Equations (JSCR, 1997)
- Schoenfeld et al. — Strength & Hypertrophy Adaptations (JSCR, 2017)
- NSCA — Essentials of Strength Training and Conditioning
- ExRx.net — Strength Standards
- Peterson et al. — Dose-Response for Strength (MSSE, 2005)
Related Calculators
Explore All Health Calculators
Track your strength progress with evidence-based fitness tools — CalculatorApp.me.
Browse Health Calculators →