One Rep Max (1RM) Calculator: Epley & Brzycki Formulas
Calculate your estimated 1-Rep Max (1RM) accurately using Epley and Brzycki equations. Includes rep percentage tables, charts, and programming tips.
TL;DR: Testing a true 1-Rep Max to failure is exhausting and carries high injury risk. Estimating your 1RM mathematically gives you accurate programming numbers while preserving your central nervous system. Use the calculator below to estimate your 1RM across Epley and Brzycki formulas.
Knowing your One-Rep Max (1RM) — the maximum weight you can lift for a single, full-range-of-motion repetition — is essential for structured strength training. Top training systems such as 5/3/1, Smolov, the Texas Method, and RPE-based powerlifting routines base their set and rep targets on percentages of your 1RM.
However, attempting a true maximal lift every week is dangerous and highly taxing on your central nervous system (CNS). This interactive calculator uses scientifically validated formulas to estimate your 1RM based on submaximal sets.
Interactive 1RM Calculator
Comparison: 1RM Formulas at a Glance
| Formula Name | Author & Year | Mathematical Equation | Best Rep Range | Key Characteristics |
|---|---|---|---|---|
| Epley Formula | Boyd Epley (1985) | 1RM = W × (1 + R/30) | 2 – 10 Reps | Standard for college strength programs; highly reliable for compound lifts. |
| Brzycki Formula | Matt Brzycki (1993) | 1RM = W × (36 / (37 - R)) | 1 – 8 Reps | Slightly more conservative; widely accepted in powerlifting and bodybuilding. |
| Lander Formula | Lander (1985) | 1RM = (100 × W) / (101.3 - 2.67123 × R) | 2 – 6 Reps | Accurate for heavy lower-rep sets near maximal capacity. |
Repetition Max (RM) Percentage Matrix
Once you calculate your 1RM, use this standard percentage breakdown table to structure your working sets across different rep targets:
| Repetition Target (RM) | Percentage of 1RM | Primary Training Adaptation | Recommended Rest Interval |
|---|---|---|---|
| 1RM | 100% | Absolute Strength Testing | 3 – 5 Minutes |
| 2RM | 95% | Maximal Neuromuscular Strength | 3 – 5 Minutes |
| 3RM | 93% | Heavy Strength Building | 3 – 4 Minutes |
| 5RM | 87% | Ideal Strength-Hypertrophy Balance | 2 – 3 Minutes |
| 8RM | 80% | Classic Hypertrophy & Muscle Building | 2 Minutes |
| 10RM | 75% | Muscle Hypertrophy & Density | 90 Seconds |
| 12RM | 70% | Muscular Endurance & Pump | 60 – 90 Seconds |
How to Use 1RM Data in Your Workouts
- Calculate Training Max (TM): Many programs (such as Jim Wendler’s 5/3/1) use a “Training Max” set at 90% of your calculated 1RM. This provides a safety buffer and prevents nervous system overtraining.
- Autoregulate with RPE: Pair your 1RM data with Rate of Perceived Exertion. If your calculated 5RM is 225 lbs, but on a given day 225 lbs feels like RPE 9.5, scale down slightly to match your recovery state.
- Track Historical Volume: Monitor your estimated 1RM over 8 to 12 week blocks to confirm that your progressive overload plan is working.
Effortless 1RM Tracking with Beau
Stop doing manual math on scrap paper or updating clumsy spreadsheets between sets.
With Beau, calculating and recording your working sets and estimated 1RM is completely automatic. You simply speak or type naturally:
“Bench press 225 lbs for 5 reps at RPE 8”
Beau’s local AI parses the load, volume, and intensity, calculates your estimated 1RM behind the scenes, and updates your progression graphs instantly.
Stay focused on your lifting. Download Beau for iOS today.