One-Rep Max Calculator (Epley/Brzycki)
Your one-rep max (1RM) is the heaviest weight you can lift for a single rep with proper form. Testing it directly carries injury risk — especially for beginners. Instead, lift a sub-maximal weight for 2–10 reps and plug the numbers in. This calculator applies three peer-reviewed formulas — Epley, Brzycki, and Lombardi — and averages them so you get a reliable estimate for programming your training zones.
When to use this calculator
- Setting training zones (60–95% 1RM) for strength programs like 5/3/1 or Texas Method
- Tracking strength progress without maxing out every session
- Calculating warm-up and working sets before a heavy training day
- Comparing relative strength across different body weights
- Preparing for a powerlifting meet attempt selection
- Estimating 1RM after returning from a deload or injury layoff
How it works
2 min readWhat is one-rep max (1RM)?
One-rep max is the maximum weight you can lift for a single repetition with proper form. Rather than test it directly—which risks injury—lifters estimate 1RM from sub-maximal loads using formulas like Epley or Brzycki. For example, lifting 225 lb for 5 reps predicts approximately 253 lb 1RM. This benchmark determines training intensities.
How It Works
All three formulas take two inputs: w (weight lifted) and r (number of reps completed). They are validated for sets of 1–10 reps; accuracy degrades noticeably above 10 reps because fatigue and aerobic capacity increasingly determine the rep count rather than pure strength.
Formulas
Epley (1985):
1RM = w × (1 + r / 30)
Brzycki (1993):
1RM = w × 36 / (37 − r)
Lombardi (1989):
1RM = w × r^0.10
Average:
1RM_avg = (Epley + Brzycki + Lombardi) / 3For r = 1 (an actual single), all three return exactly w, so the calculator handles true max attempts correctly.
Worked Example
Lifter squats 225 lb × 5 reps:
| Formula | Calculation | Estimated 1RM |
|---|---|---|
| Epley | 225 × (1 + 5/30) | 262.5 lb |
| Brzycki | 225 × 36 / (37−5) | 253.1 lb |
| Lombardi | 225 × 5^0.10 | 251.5 lb |
| Average | (262.5 + 253.1 + 251.5) / 3 | 255.7 lb |
Training percentages from the 255.7 lb average:
| % | Weight |
|---|---|
| 50% | 127.8 lb |
| 60% | 153.4 lb |
| 70% | 179.0 lb |
| 80% | 204.6 lb |
| 85% | 217.3 lb |
| 90% | 230.1 lb |
| 95% | 242.9 lb |
When NOT to Apply / Limitations
Frequently asked questions
Which formula is most accurate — Epley, Brzycki, or Lombardi?
Research shows Epley and Brzycki perform similarly for 3–8 rep ranges on compound lifts (within 2–3% of tested 1RM). Lombardi tends to predict slightly lower. Averaging the three reduces formula-specific bias. No single formula is universally superior across all lifters and exercises.
How many reps should I use for the most accurate estimate?
3–5 reps with a weight that genuinely challenges you gives the best accuracy. Accuracy drops as reps climb above 8–10 because muscular endurance starts to dominate. A 3RM set is often the sweet spot — challenging without excessive fatigue.
Can I use this for deadlifts and overhead press, not just bench and squat?
Yes. The formulas are formula-agnostic — they only use weight and reps. They have been validated most thoroughly on bench press and squat, but are commonly applied to deadlift, overhead press, and barbell row with similar reliability.
Should I use the Epley, Brzycki, or Average 1RM to program my sets?
Use the Average 1RM for programming unless you have a reason to prefer one formula. Averaging reduces the impact of any single formula's error. Many strength coaches default to Epley for historical consistency, which is also acceptable.
My Epley and Brzycki results are very different. Why?
The two formulas converge closely for 3–6 reps but diverge more at higher rep counts (8–10+). If you see a >5% gap, your rep count is likely too high for reliable 1RM prediction. Redo the test with a heavier weight for 3–5 reps.
Are these percentages the same as RPE-based programming?
Not exactly. Percentage-based training (e.g., 80% × 3 sets × 5 reps) and RPE (Rate of Perceived Exertion) are related but distinct systems. Your 80% 1RM on a good day may feel like RPE 7–8; on a fatigued day it could feel like RPE 9. Many modern programs combine both.
Does 1RM change day to day?
Yes. Sleep, nutrition, hydration, stress, and cumulative training fatigue all affect your actual 1RM on any given day. Treat the estimate as a training baseline — not a fixed number — and adjust loads based on how the bar moves and how you feel.
Is it safe to test my actual 1RM instead of estimating?
For experienced lifters with solid technique and a spotter, direct 1RM testing is standard practice. For beginners or those returning from injury, estimated 1RM from a 3–5RM set is safer. Always use proper warm-up sets (50%, 70%, 85%, 93% before an attempt).
How do I convert between lb and kg in this calculator?
Select your unit before entering the weight. The calculator keeps all outputs in the same unit you enter. To convert manually: 1 kg = 2.2046 lb; 1 lb = 0.4536 kg.
How often should I re-estimate my 1RM?
Re-test every 4–8 weeks or at the end of a training block. Significant strength gains (a new 5RM PR, for example) mean your old 1RM estimate is stale and your training percentages should be recalculated.
Sources and references
- Epley B. (1985). Poundage Chart. Boyd Epley Workout.
- Brzycki M. (1993). Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue. Journal of Physical Education, Recreation & Dance.
- LeSuer D.A. et al. (1997). The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift. Journal of Strength and Conditioning Research.
- NSCA — Essentials of Strength Training and Conditioning, 4th Ed.