Strength Prophet — 1RM Calculator
Predict your one-rep max with the Brzycki formula and get an instant warm-up plan.
Warm-Up Set Generator
| Set | Intensity | Suggested Weight | Reps | Rest |
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How to Use This 1RM Calculator
- Select Pounds (lb) or Kilograms (kg)
- Enter the weight you lifted for a specific exercise (e.g., bench press, squat)
- Enter the number of reps you performed (best accuracy with 1–10 reps)
- Select rounding preference (standard or exact)
- View your estimated One-Rep Max (1RM) and warm-up set guide
Formula Used (Brzycki)
The calculator uses the Brzycki formula, which is one of the most reliable for estimating 1RM from submaximal lifts:
1RM = Weight Lifted × 36 ÷ (37 − Reps Performed)
Real Example
You lifted: 225 lb for 5 reps
Calculation: 225 × 36 ÷ (37 − 5) = 225 × 36 ÷ 32 = 253.125 lb
Result: Estimated 1RM ≈ 255 lb (rounded)
Why Use Our 1RM Calculator?
- ✅ Accurate & Proven — Uses the Brzycki formula, validated in strength research
- ✅ Free & Unlimited — No signup, no hidden limits
- ✅ Instant Warm-Up Plan — Get suggested weights for 50%, 70%, and 90% of your 1RM
- ✅ Works for Any Exercise — Bench press, squat, deadlift, overhead press, etc.
- ✅ Mobile Friendly — Use it at the gym on your phone
Frequently Asked Questions
How accurate is the 1RM calculator?
The Brzycki formula is most accurate for 1–10 reps. For 10+ reps, the estimate becomes less precise. For best results, test with a weight you can lift for 3–8 reps.
Can I use this for any exercise?
Yes — bench press, squat, deadlift, shoulder press, pull-ups, and any other barbell or dumbbell exercise.
Do I need to test my actual 1RM?
No — that’s the point. You can estimate your 1RM safely without attempting a maximal lift, reducing injury risk.
What’s the difference between rounding options?
Standard rounding rounds to the nearest 5 lb (or 2.5 kg) — practical for gym plates.
Exact shows the raw calculated number.
Related Fitness Calculators
- BMI Calculator — Check your body mass index
- Calorie Burn Calculator — Estimate calories burned during exercise
- One-Rep Max (1RM) Calculator — Alternate version
- BMR Calculator — Find your basal metabolic rate
Disclaimer: This 1RM calculator provides estimates only. Actual strength varies based on fatigue, technique, and individual factors. Always use a spotter and proper form when lifting heavy. Consult a fitness professional before starting any new training program.