One Rep Max Calculator

Your one-rep max (1RM) is the maximum weight you can lift for a single repetition. Knowing it lets you set percentage-based training loads precisely — essential for strength and powerlifting programs.

How to Use This Calculator

1. Enter the weight lifted.
2. Enter the number of reps performed (at that weight, to near failure).
3. Select the formula: Epley, Brzycki, Lander, O'Conner, or average of all.
4. Click Calculate to see estimated 1RM and a percentage table (50%–100% of 1RM).

1RM Estimation Formulas

Epley: 1RM = weight × (1 + reps/30)

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

Lander: 1RM = (100 × weight) / (101.3 − 2.67123 × reps)

These formulas are most accurate at 1–10 reps. Beyond 10 reps, accuracy decreases significantly.

Example Calculation

Bench press: 185 lbs for 5 reps

• Epley: 185 × (1 + 5/30) = 185 × 1.167 = 215.9 lbs
• Brzycki: 185 × 36/32 = 207.2 lbs
• Average estimated 1RM: ≈ 210 lbs

Training Percentage Guide

• 90–100% 1RM: Maximal strength, 1–3 reps
• 80–90%: Heavy strength training, 3–5 reps
• 70–80%: Hypertrophy/strength mix, 6–10 reps
• 60–70%: Hypertrophy, 10–15 reps
• 50–60%: Endurance/technique, 15–20+ reps

Common Mistakes to Avoid

• Testing 1RM too frequently — True 1RM testing is very taxing. Estimate from submaximal sets instead, and test actual 1RM only at program peaks.
• Using estimated 1RM as definitive — These formulas have ±5–10% error margins. Treat them as training guides, not absolute numbers.
• Basing percentages on a stale 1RM — As you get stronger, update your estimated 1RM every 4–6 weeks. Using outdated numbers means undertrained or overtrained programming.

Frequently Asked Questions

Is testing your actual 1RM safe?

Yes, with proper warm-up, technique, and spotters. However, for most recreational lifters, estimated 1RM from submaximal sets is safer and adequate for programming purposes.

How often should I increase my 1RM?

Beginners may increase weekly. Intermediate lifters monthly. Advanced lifters every 3–6 months. Use your estimated 1RM trend to gauge progress — consistent increases mean your program is working.

Can I use this for any lift?

Yes — bench press, squat, deadlift, overhead press, or any barbell lift. The formulas don't distinguish between exercises, though accuracy varies slightly by lift and individual muscle fiber composition.

Conclusion

Knowing your 1RM is the foundation of percentage-based strength programming. Use this calculator to estimate it safely from any submaximal set, then use the percentage table to program your training loads precisely.

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