Enter weight & reps
Input the weight you lifted and how many clean reps you completed.
Free One Rep Max Calculator
Find out your estimated One Rep Max (1RM) without attempting a dangerous heavy lift. Just enter the weight you lifted and how many reps you did.
How to use it
How to calculate your 1RM
Use a recent, challenging set (between 2 and 10 reps) for the most accurate estimation.
Reference
The numbers behind the tool.
Formulas, reference tables, and practical guidance you can come back to.
Percentage of 1RM Chart
The One-Repetition Maximum (1RM) is universally recognized in strength and conditioning as the gold standard for measuring absolute muscular strength. It represents the maximum amount of weight an individual can lift for a single repetition of a given exercise with proper technique. Knowing your 1RM is essential for designing effective, periodized resistance training programs, as coaches and athletes use specific percentages of this maximum value to target different physiological adaptations, such as muscular endurance (lower percentage), hypertrophy, or maximal strength (higher percentage).
While directly testing a true 1RM can provide an exact measurement, it also places immense stress on the central nervous system and connective tissues, increasing the risk of injury, especially for novice lifters. Predictive 1RM calculators solve this problem by utilizing scientifically validated formulas, such as the Brzycki, Epley, or Lombardi equations, to estimate maximal strength based on submaximal lifting data (e.g., lifting a lighter weight for 5 to 10 repetitions). This approach offers a safer, yet highly reliable method to gauge strength progress and calibrate training loads without the need for frequent, grueling maximal exertion tests.
| Reps | Percent of 1RM |
|---|---|
| 1 | 100% |
| 2 | 95% |
| 4 | 90% |
| 6 | 85% |
| 8 | 80% |
| 10 | 75% |
FAQ
Frequently asked questions.
Quick answers about this tool and how to train with it.
Which formula is used?
This calculator primarily uses the Epley formula: 1RM = Weight × (1 + (Reps / 30)), which is standard across the fitness industry.
Is the estimate accurate for high reps?
Not usually. 1RM formulas become less accurate when estimating from sets above 10 reps. For best results, use a 3-5 rep max.
Is it safe to attempt a true 1RM?
Attempting a true 1RM can be safe if you have excellent technique, a solid strength foundation, and experienced spotters or safety equipment. However, for beginners or those training alone, predicting your 1RM using a 3-5 rep max test is significantly safer and provides nearly identical data for program design. Always prioritize form over the weight on the bar.
Which 1RM formula is most accurate?
The Epley and Brzycki formulas are widely regarded as the most accurate for predicting 1RM across general populations. However, all formulas become less accurate when you input sets of more than 10 repetitions, as endurance factors begin to skew the results. For the best accuracy, use a heavy weight you can lift for only 3 to 5 reps.
How should I use my 1RM for programming?
Your 1RM serves as a baseline to calculate specific training percentages based on your goals. For example, training at 70-80% of your 1RM is typically ideal for muscle hypertrophy, while 85-95% is optimal for building maximal strength. Re-testing or re-calculating your 1RM every few months helps ensure your program continues to provide adequate stimulus.
Keep going
Related tools & further reading.
More free tools that pair well with this one, plus guides and articles to go deeper.
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Track your strength progress.
CounterUps provides advanced analytics so you can watch your estimated 1RM increase over time.