How to Calculate Your One Rep Max (1RM) - Complete Guide with Epley & Brzycki Formula & Examples

Your One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise with proper form. This metric is fundamental for weightlifters, powerlifters, and strength athletes because it establishes your absolute strength baseline for exercises like bench press, squat, deadlift, and overhead press.

Knowing your 1RM allows you to structure training programs using percentage-based loading. For example, if your 1RM bench press is 225 lbs, training at 80% means lifting 180 lbs. This precision helps optimize hypertrophy, strength gains, and performance while reducing injury risk from guessing weights.

However, testing your actual 1RM carries injury risk, especially for beginners. This is why 1RM calculators using proven formulas like Epley and Brzycki are invaluable—they let you estimate your maximum based on lighter, safer rep ranges (typically 2-10 reps).

The most widely used 1RM formulas are the Epley formula and the Brzycki formula. Both estimate your one rep max based on the weight lifted and the number of repetitions completed.

Epley Formula:
1RM = weight × (1 + reps/30)

Example: If you bench press 200 lbs for 5 reps:
1RM = 200 × (1 + 5/30) = 200 × 1.167 = 233 lbs

Brzycki Formula:
1RM = weight × (36 / (37 - reps))

Example: Same 200 lbs for 5 reps:
1RM = 200 × (36 / (37 - 5)) = 200 × (36/32) = 225 lbs

Our calculator uses both formulas and averages them for a more accurate estimate. The Epley formula tends to slightly overestimate at higher rep ranges, while Brzycki is more conservative. Using both provides a balanced prediction.

Example 1 - Bench Press:
You squat 315 lbs for 4 reps.
- Epley: 315 × (1 + 4/30) = 315 × 1.133 = 357 lbs
- Brzycki: 315 × (36 / 33) = 315 × 1.091 = 343 lbs
- Average 1RM estimate: 350 lbs
This means your training at 85% would be around 298 lbs.

Example 2 - Deadlift:
You deadlift 405 lbs for 3 reps.
- Epley: 405 × (1 + 3/30) = 405 × 1.10 = 446 lbs
- Brzycki: 405 × (36 / 34) = 405 × 1.059 = 429 lbs
- Average 1RM estimate: 438 lbs
Your 5-rep training weight at 90% would be approximately 394 lbs.

Example 3 - Overhead Press:
You overhead press 135 lbs for 8 reps.
- Epley: 135 × (1 + 8/30) = 135 × 1.267 = 171 lbs
- Brzycki: 135 × (36 / 29) = 135 × 1.241 = 168 lbs
- Average 1RM estimate: 170 lbs
This helps you plan your 3-rep sets at 92% (~156 lbs).

1. Using too many repetitions: Form breakdown becomes likely after 10 reps, making the estimate unreliable. Stick to 1-10 rep ranges for best accuracy.

2. Not accounting for exercise-specific variations: Your 1RM differs significantly between exercises. Don't assume your bench press 1RM applies to your squat or deadlift.

3. Failing to warm up properly: Cold muscles produce weaker results. Always complete a thorough warm-up before your working set used for 1RM calculation.

4. Using fatigued training sessions: Calculate 1RM when fresh, not at the end of a grueling workout. Your results will underestimate your true maximum.

5. Over-relying on a single test: 1RM estimates vary day-to-day. Test multiple times over weeks and track the trend rather than fixating on one number.

6. Ignoring the margin of error: These formulas estimate within 5-10% accuracy. A 350 lbs estimate could realistically be 315-385 lbs. Use it as a starting point, not absolute truth.