One Rep Max Calculator
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition with proper form. Testing a true 1RM requires maximal effort and carries injury risk, especially for beginners. Submaximal estimation lets you predict your 1RM from a lighter set — a safer and more practical approach for program design.
This calculator accepts the weight you lifted and the number of reps completed, then applies two widely used formulas: Epley and Brzycki. Both predict your theoretical maximum from submaximal performance, and comparing the two gives you a reasonable range for planning training loads.
Results work best for sets of 1 to 10 reps with good technique. The included training percentage table translates your estimated 1RM into working weights for hypertrophy, strength, and power phases — a cornerstone of structured resistance training programs.
Results update instantly as you change your inputs.
Your Result
Epley estimate
Brzycki estimate
112.5 kg
Training percentages
| % of 1RM | Epley formula | Brzycki formula |
|---|---|---|
| 50% | 58.3 kg | 56.3 kg |
| 55% | 64.2 kg | 61.9 kg |
| 60% | 70 kg | 67.5 kg |
| 65% | 75.8 kg | 73.1 kg |
| 70% | 81.7 kg | 78.8 kg |
| 75% | 87.5 kg | 84.4 kg |
| 80% | 93.3 kg | 90 kg |
| 85% | 99.2 kg | 95.6 kg |
| 90% | 105 kg | 101.3 kg |
| 95% | 110.8 kg | 106.9 kg |
1RM estimation formulas
The Epley formula, published by Boyd Epley in 1985, estimates one-rep max as weight multiplied by (1 + reps ÷ 30). It is one of the most commonly used equations in strength coaching because of its simplicity and reasonable accuracy across a range of exercises and rep counts. Epley tends to produce slightly higher estimates at higher rep ranges compared to some alternatives.
The Brzycki formula, developed by Matt Brzycki, calculates 1RM as weight multiplied by (36 ÷ (37 − reps)). It was derived from regression analysis on college athletes and generally produces conservative estimates that align well with actual tested maxes in the 1 to 10 rep range. When Epley and Brzycki diverge, the average or lower value is often a safer training reference.
Both formulas assume you lifted to near-failure — the weight was challenging and you could not have completed many more reps with good form. Sets stopped well short of failure (three or more reps in reserve) will underestimate your true 1RM. For best accuracy, use a weight you can lift for 3 to 8 reps while maintaining technique.
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × (36 ÷ (37 − reps))
Using your 1RM estimate in training
Your estimated 1RM is a programming tool, not a number you need to test in the gym. Use it to set working weights as percentages of max. Training at 65 to 75 percent of 1RM for 8 to 12 reps is a classic hypertrophy range. Strength work typically falls between 80 and 90 percent for 1 to 5 reps, while power development may use 50 to 70 percent with explosive intent.
The training percentage table shows corresponding weights from 50 to 95 percent of your estimated max. Start new programs at the lower end of your target range and progress gradually. If prescribed reps feel too easy or too hard, adjust by 2.5 to 5 kg rather than recalculating your entire max.
Different lifts have different 1RM values — your squat max is not your bench max. Calculate separately for each main exercise you program. Also note that 1RM estimates from isolation movements (bicep curls, lateral raises) are less reliable because fatigue patterns differ from compound lifts.
Retest your submaximal input every 4 to 8 weeks as you get stronger. A weight that was a hard 5 reps last month may become an easy 8 reps today, meaning your true max has increased even if the scale weight on the bar stayed the same.
Frequently asked questions about 1RM
What is a one rep max (1RM) calculator?
A one rep max calculator estimates the heaviest weight you could lift for a single repetition based on a submaximal set. Enter the weight you lifted and how many reps you completed — the Epley and Brzycki formulas extrapolate your max without testing a true 1RM, which reduces injury risk for most gym trainees.
Which formula is more accurate, Epley or Brzycki?
Both perform similarly for sets of 1 to 10 reps on compound lifts. Brzycki tends to be slightly more conservative, while Epley may overestimate at higher rep counts. Using the average of both estimates, or the lower value for safety, is a common coaching practice. Actual accuracy depends on the individual, exercise, and how close to failure the set was taken.
Why are results unreliable above 10 reps?
At higher rep counts, local muscular endurance, cardiovascular fitness, and pain tolerance influence performance more than maximal force production. Formulas were validated primarily on sets of 1 to 10 reps where the relationship between submaximal load and true max is most linear. A set of 15 reps at moderate weight tells you little about your absolute strength ceiling.
How often should I update my 1RM estimate?
Recalculate every 4 to 8 weeks during a training block, or whenever your working weights feel significantly easier than prescribed. You do not need to test with the exact same rep count each time — any set of 3 to 8 reps near failure provides a valid input. Consistent progression in working weights is often more useful than obsessing over the exact 1RM number.
Can I use 1RM percentages for all exercises?
Percentages work best for main compound lifts like squat, bench press, and deadlift where you can reliably push near failure. For accessory movements, RPE (rate of perceived exertion) or rep targets are often more practical because isolation exercises fatigue differently and true 1RM testing is impractical or unsafe for many of them.
What training percentage should I use for muscle growth?
Research supports hypertrophy across a wide range — roughly 30 to 85 percent of 1RM when sets are taken close to failure. The traditional 65 to 75 percent range for 8 to 12 reps is a reliable starting point. Higher reps at lower percentages (60 percent for 15 to 20 reps) can also build muscle if sets are challenging. Total volume and proximity to failure matter more than the exact percentage.
Should beginners estimate or test their 1RM?
Beginners should avoid true 1RM testing because technique under maximal loads is not yet established. Submaximal estimation from a moderate set of 5 to 8 reps is safer and sufficient for program design. Focus on learning movement patterns with lighter loads first, then use this calculator once you can perform compound lifts with consistent form at working weights.
Limitations of 1RM formulas
All submaximal formulas become unreliable above 10 reps because muscular endurance factors dominate over maximal strength. Fast-twitch dominant lifters may exceed formula predictions, while endurance-oriented athletes may fall short. Exercise selection, lifting tempo, and rest periods between sets also affect how many reps you can perform at a given weight.
Never attempt a true one-rep max without proper warm-up, spotters, and experience. Estimated values are for program planning only and should not encourage reckless maximal attempts, especially on technical lifts like the deadlift or overhead press.
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