One Rep Max Calculator
Calculate your one-rep maximum (1RM) for any exercise using proven formulas
The One Rep Max (1RM) Calculator estimates the maximum weight you can lift for a single repetition of any exercise. This tool uses scientifically validated formulas to predict your 1RM based on submaximal lifts, helping you plan training programs, track strength progress, and set realistic goals. It's essential for powerlifters, bodybuilders, and anyone serious about strength training.
Lift Information
Number of reps completed to failure or near failure
How hard did the set feel? (10 = maximum effort)
One Rep Max Results
All Formula Results
Training Percentages
Rep Max Predictions
Training Recommendations
Strength Standards
How to Use
1. Select the exercise you performed
2. Enter the weight you lifted
3. Input the number of repetitions completed
4. Rate your perceived exertion (RPE)
5. Choose a calculation formula
6. Click "Calculate 1RM" to see results
7. Review training percentages and recommendations
8. Use results to plan your training program
1RM Formulas Explained
Epley Formula:
1RM = Weight × (1 + 0.0333 × Reps)
Most widely used and accurate for 1-10 reps
Brzycki Formula:
1RM = Weight ÷ (1.0278 - 0.0278 × Reps)
Good for higher rep ranges (1-15 reps)
Lombardi Formula:
1RM = Weight × Reps^0.10
Conservative estimate, good for beginners
Average Method:
Uses multiple formulas and averages the results for a more balanced estimate
RPE Scale Guide
RPE 10:
Maximum effort - could not do another rep
RPE 9:
Could have done 1 more rep
RPE 8:
Could have done 2 more reps
RPE 7:
Could have done 3 more reps
Why RPE Matters:
RPE adjusts the calculation based on how close to failure you were, improving accuracy
Training Applications
Strength Training:
Use 85-95% of 1RM for 1-5 reps to build maximum strength
Power Training:
Use 75-85% of 1RM for 3-6 reps with explosive movement
Hypertrophy:
Use 65-80% of 1RM for 6-12 reps to build muscle mass
Endurance:
Use 50-65% of 1RM for 12+ reps to build muscular endurance
Program Planning:
Use 1RM to set appropriate loads for different training phases
Safety Guidelines
Warm-Up Properly:
Always perform a thorough warm-up before attempting heavy lifts
Use a Spotter:
Have a qualified spotter when attempting near-maximal loads
Progressive Loading:
Work up to your 1RM gradually over several sets
Listen to Your Body:
Don't attempt a 1RM if you're feeling fatigued or unwell
Recovery:
Allow adequate recovery time between 1RM attempts (1-2 weeks minimum)
Frequently Asked Questions
How accurate are 1RM calculators?
Generally accurate within 5-10% for most people, but individual variation exists. Best accuracy with 1-10 rep tests.
Should I test my actual 1RM?
Only if you're experienced, have proper supervision, and it's necessary for your sport or goals.
How often should I update my 1RM?
Test or calculate every 4-6 weeks to track progress and adjust training loads accordingly.