One-Rep Max (1RM) Calculator
Estimate your maximum strength for weightlifting exercises based on the weight you can lift for multiple repetitions.
Estimated One-Rep Max
Based on your inputs
Formula Comparison
About One-Rep Max
One-rep max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise.
Epley Formula: 1RM = w × (1 + r/30)
Brzycki Formula: 1RM = w × (36 / (37 – r))
Lombardi Formula: 1RM = w × r^0.1
O’Conner Formula: 1RM = w × (1 + r/40)
Wathan Formula: 1RM = w × (100 / (48.8 + (53.8 × e^(-0.075 × r))))
Where w is the weight lifted, and r is the number of repetitions performed.
These formulas provide estimates that are generally within 2-3% of your actual 1RM when tested with proper form.
Training Applications of 1RM:
- Strength Training: 85-100% of 1RM for 1-6 reps
- Hypertrophy Training: 67-85% of 1RM for 6-12 reps
- Endurance Training: Below 67% of 1RM for 12+ reps
- Program Planning: Used to set appropriate training weights
- Progress Tracking: Measure strength gains over time
- Peaking Programs: Used to plan competition attempts
It’s recommended to recalculate your 1RM every 4-8 weeks as your strength changes.
Safety Tips for 1RM Testing:
- Always warm up properly before attempting heavy lifts
- Use a spotter when attempting maximal weights
- Progress gradually in weight increases
- Maintain proper form throughout the movement
- Listen to your body and stop if you feel sharp pain
- Don’t test your 1RM too frequently (4-8 week intervals)
- Consider using safety equipment (power rack, collars)
- Stay hydrated and ensure proper nutrition on testing days
Remember that estimated 1RM values are guides – actual maximum attempts should be approached with caution.