1RM Calculator
Estimate your one rep max with six estimation formulas, see training percentages for every rep range, and find out where you rank on the strength-standards scale.
Formula Comparison
Each formula gives a slightly different estimate. Our headline number is the average.
Training Percentages
What to load for common rep targets, based on your estimated 1RM.
| Target | Weight | % of 1RM |
|---|
Strength Standards
Based on a percentage of bodyweight. Values approximate widely-cited ExRx and Symmetric Strength ranges.
The Six Formulas
Each formula estimates a one-repetition maximum from the same weight and repetition count. The headline is their arithmetic average. Averaging does not guarantee reduced bias or a particular error margin. Your exercise, technique, fatigue and the effort of the recorded set can affect how useful an estimate is.
What does 100 kg for 5 reps estimate?
Before display rounding, Epley gives 100 × (1 + 5/30) = 116.7 kg. Brzycki gives 100 × 36 / (37 - 5) = 112.5 kg. The same set produces different estimates because the equations differ. The calculator shows all six outputs so you can inspect that spread, rounding displayed loads to the nearest 0.5 unit.
The spread is not a confidence interval or proof that your true maximum falls inside it. Use the estimate as a planning reference, and keep the exercise, technique and set conditions consistent when tracking it over time.
How is a strength tier different from an estimated 1RM?
An estimated 1RM converts a completed set into a possible single-rep load. A strength tier compares that load with a bodyweight-based reference. You can inspect the separate strength standards calculator for that comparison. Its categories are reference labels, not a personalized training prescription.
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What else should you know?
What is a 1RM?
A one-repetition maximum is the heaviest load you can lift once with the defined technique for an exercise. This calculator estimates it from a completed set. An estimated value is a planning reference and does not confirm that you can safely lift that load today.
How accurate are 1RM calculators?
There is no universal error margin for every person, exercise and repetition count. Technique, fatigue, effort and muscular endurance can affect an estimate. Record the conditions of the set and follow the trend consistently. Avoid treating an estimated maximum as a load you must attempt.
Which 1RM formula is most accurate?
No formula is guaranteed to be most accurate for every lifter and exercise. This calculator displays six estimates and uses their arithmetic average for its headline. The average does not guarantee reduced bias. Inspect the spread and use the same method when comparing sessions.
What are strength standards?
Strength standards compare a load with a reference category, often relative to bodyweight and grouped by exercise and sex. They answer a different question from estimating a maximum. The categories provide context, but they cannot determine your personal training readiness, technique quality or recovery needs.
How should I use the training percentage table?
The table multiplies the estimated maximum by preset percentages. Those loads are starting references rather than guaranteed repetition targets or a complete program. Select working weights according to your plan, technique and current capacity. If the estimate changes, review the underlying set before changing every training load.
Track strength and physique together
GainFrame brings your training record and progress photos together so you can review strength and visible changes over time.
- Body fat, FFMI, and muscle scores from a photo
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