One-Rep Max Calculator
Calculate your estimated one-rep maximum using proven formulas from strength training research. Perfect for powerlifting, weightlifting, and strength programming.
1RM Calculation
Enter your lift weight, repetitions, and select a formula to calculate your one-rep max
reps (1-10)
1RM = W × (1 + r ÷ 30)
Most commonly used, good for 1-10 reps
1RM = W × 36 ÷ (37 − r)
Conservative estimate, best for 2-10 reps
1RM = W × r^0.10
Based on power function, good for all rep ranges
Estimated 1RM
Enter weight and reps to calculate your one-rep max.
About One-Rep Max Testing
Formula Comparison
- Epley: Most popular, linear progression
- Brzycki: More conservative, asymptotic curve
- Lombardi: Power function, works across all rep ranges
- Accuracy: All formulas are within ~10% of actual 1RM
Best Practices
- Use weights you can lift for 3-8 reps for best accuracy
- Ensure proper form throughout the test set
- Rest adequately between attempts
- Test when fresh, not after other training
Safety Considerations
- Warm-up: Always perform proper warm-up sets
- Spotter: Use a spotter for bench press and squats
- Progressive: Work up gradually to test weight
- Recovery: Allow adequate recovery between max efforts
Using Your 1RM
| % of 1RM | Purpose |
|---|---|
| 50-60% | Speed/Power |
| 65-75% | Hypertrophy |
| 80-90% | Strength |
| 90-100% | Max Strength |
How to Use This Calculator
Step-by-step guide to get accurate results
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What is a One Rep Max (1RM) Calculator?
A One Rep Max Calculator (also called a 1RM Calculator Online or One Repetition Maximum Calculator) is a strength-training tool that estimates the maximum weight you can lift for one single repetition of an exercise. Instead of testing your absolute max lift in the gym which can be risky, you can calculate one rep max free by inputting the weight you lifted and the number of reps performed.
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Why is Calculating Your 1RM Important?
Set Training Loads
Accurately adjust loads for strength, hypertrophy, or endurance.
Track Progress
Monitor improvements in bodybuilding, CrossFit, Olympic lifting, and powerlifting.
Prevent Overtraining
Stay safe by lifting within optimal intensity ranges.
Customize Programs
Apply to 5x5 training, progressive overload, and hypertrophy cycles.
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Popular One Rep Max Formulas Explained
Epley Formula
1RM = Weight × (1 + 0.0333 × Reps). Best for general lifters. Simple and accurate up to 10 reps but less accurate at very high reps.
Brzycki Formula
1RM = Weight × (36 ÷ (37 − Reps)). Good for strength and hypertrophy. Reliable under 10 reps but may underestimate for endurance sets.
Lombardi Formula
1RM = Weight × Reps^0.10. Popular among powerlifters. Works across wide rep ranges but may overestimate for beginners.
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Safe Ways to Calculate 1RM Without Max Lifting
Choose Moderate Weights
Lift 3–10 reps with proper form instead of maxing out.
Log Data
Record the exact weight and repetitions performed.
Use Percentage Charts
Estimate training loads at 50%, 60%, 70%, 80%, 90% safely.
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How to Use 1RM in Training Programs
Strength Training
Train at 80–90% of 1RM for 1–5 reps. Best for powerlifting, Olympic lifting, and CrossFit.
Hypertrophy (Muscle Growth)
Train at 65–75% of 1RM for 6–12 reps. Effective for bodybuilding and size gains.
Endurance & Conditioning
Train at 50–65% of 1RM for 12–20+ reps. Great for general fitness and functional training.
Examples
5x5 Workout (~75–85%), Progressive Overload (increase gradually), Hypertrophy Training, CrossFit strength-conditioning.
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Best Practices, Safety & Disclaimers
Warm Up
Always warm up before testing or estimating.
Never Max Alone
Use a spotter or safety equipment.
Start Conservatively
Beginners should lift cautiously.
Lift-Specific Adjustments
Apply separately for bench, squat, deadlift, Olympic lifts.
Listen to Your Body
Avoid lifting through pain.
Frequently Asked Questions
What is the most accurate One Rep Max formula?
The Epley 1RM Formula Calculator is most accurate for lifts under 10 reps. Brzycki works well for moderate reps, while Lombardi suits powerlifters.
Can beginners use a One Rep Max Calculator?
Yes, beginners should avoid true max attempts and instead use submaximal lifts (3–10 reps) for safe estimates.
How often should I recalculate my 1RM?
Most lifters update results every 6–8 weeks. Advanced athletes may recalculate more often during strength cycles.
Is it safe to test my true one rep max in the gym?
It can be risky without a spotter or proper equipment. Using a 1RM Calculator is safer and effective.
How do I use my 1RM to program workouts?
Use a One Rep Max Percentage Calculator: 50–65% endurance, 65–75% hypertrophy, 75–85% strength, 85–95% power.
Does this calculator work for all exercises?
Yes, it works for bench press, squat, deadlift, military press, Olympic lifts, and accessory movements.
Can I use this tool on mobile or in the gym?
Yes, this free 1RM Calculator is optimized for mobile, desktop, and gym use worldwide.