Free One Rep Max Calculator Online
1RM via 3 formulas + full training percentage table
Your One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form — the gold standard for measuring strength. Rather than attempting a true max lift (which carries injury risk), this calculator estimates it from a submaximal set using three established formulas, then generates a full training percentage table for programming your workouts.
Frequently Asked Questions
About the One Rep Max
One Rep Max testing provides the foundation for evidence-based strength programming. Once you know your 1RM, you can prescribe specific training loads as percentages — rather than guessing whether a weight "feels hard enough."
The three formulas (Epley, Brzycki, Lombardi) each produce slightly different estimates. Accuracy is highest when the rep count is 1–5; beyond 10 reps, the formulas diverge significantly and become less reliable. For best results, test with a weight you can lift for 3–6 reps with excellent form.
True 1RM testing should only be performed by experienced lifters with proper warmup and a spotter. Submaximal estimation provides a safer and often sufficient alternative for most training contexts.
Formula Used
Epley: 1RM = Weight × (1 + Reps/30)
Brzycki: 1RM = Weight × 36/(37 - Reps)
When Should You Use This?
The One Rep Max is ideally suited for fitness enthusiasts, healthcare professionals, and individuals monitoring their health who need to perform quick, accurate calculations related to general calculations. Use this tool when you need to verify figures, compare different scenarios, or get a precise answer without manual computation errors.
What Does The Result Mean?
The calculated metrics provide a scientifically validated baseline for your health or fitness goals. While these numbers are highly accurate based on standard medical formulas, they should serve as a guide rather than a replacement for professional medical advice.
Example Calculation
Estimating 1RM from a 5-rep set at 100 kg
📥 Inputs
- Weight lifted: 100 kg
- Reps completed: 5
🔢 Calculation Steps
- 1Epley formula: 1RM = 100 × (1 + 5/30) = 100 × 1.167 = 116.7 kg
- 2Brzycki formula: 1RM = 100 × 36 / (37 − 5) = 100 × 36/32 = 112.5 kg
- 3Lombardi formula: 1RM = 100 × 5^0.10 = 100 × 1.175 = 117.5 kg
- 4Average of three formulas: (116.7 + 112.5 + 117.5) / 3 ≈ 115.6 kg
- 5Training percentages from 115.6 kg: 70% = 80.9 kg | 80% = 92.5 kg | 90% = 104.0 kg
Limitations of this Calculator
- Formulas are based on population averages and may not perfectly reflect individuals with extreme muscle mass or atypical body compositions.
- Does not replace a physical examination or clinical diagnosis by a certified medical professional.
- Calculations cannot account for underlying metabolic conditions or genetic factors that influence individual health metrics.
How to Use the One Rep Max
- 1Enter your values into the One Rep Max input fields above.
- 2Review the input labels to ensure you are using the correct units.
- 3Click the "Calculate" button to get your instant result.
- 4Use the step-by-step breakdown to understand how the result was calculated.
- 5Export or copy your result to use in reports or share with others.
Tips & Best Practices
- Train at 70-85% of 1RM for hypertrophy (muscle growth) and 85-95% for maximum strength development.
- Double-check your input units before calculating — using the wrong unit is the most common source of errors.
- Bookmark this One Rep Max for quick access next time you need it.
- Use the share button to send your results to a colleague or save them for later reference.
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⚠️ Health Disclaimer: Results provided by this calculator are for informational and educational purposes only. They do not constitute medical advice. Always consult a qualified healthcare professional, doctor, or registered dietitian before making any health, fitness, or dietary decisions.