YOUR LIFT
Calculate your one-rep max
Enter the weight you lifted and the number of clean reps you completed.
An estimate for training, not a tested maximum.
Training weights
| Intensity | Target weight | What it means |
|---|
Percentage weights are based on the Epley estimate and are rounded to one decimal. They aren't personalized prescriptions.
Primary muscles are highlighted in teal.
PRIMARY MUSCLES
How to perform the leg extension
- Align the machine pivot with your knees and place your shins behind the pad.
- Straighten your knees to lift the weight without swinging.
- Lower back down slowly and keep your hips against the seat.
Muscles worked
Main focus: Quadriceps
Also involved: Hip flexors stabilize position
Form tip
Align the machine hinge with the knee and move smoothly.
Common mistake
Kicking the load up with momentum or slamming the stack.
Safety and setup
Adjust the pad and use a comfortable range of motion.
Line up the machine pivot with your knee joint.
Record the same equipment, setup and range of motion when comparing your estimated maximum over time.
This calculator uses the total external load you enter. For dumbbell exercises, use the weight per dumbbell and be consistent when comparing workouts. For machine exercises, keep the same machine and setup, because stacks and leverage differ.
Related exercises
UNDERSTAND YOUR RESULT
What is a one-rep max?
Your one-repetition maximum (1RM) is the greatest weight you can lift once with proper form for a particular exercise. You can estimate it without attempting a heavy single: enter the weight and reps from a challenging set.
Our default estimate uses the Epley formula. We also show the Brzycki estimate so you can see that there isn't one exact formula for every lifter. The estimates become less dependable as repetitions rise, especially if the set wasn't close to your actual limit.
How accurate is a 1RM calculator?
It's a useful starting point for planning, not a guarantee of what you can lift. Rep technique, training experience, fatigue, equipment, and proximity to failure all matter. Use a recent, consistent set, ideally around 3–6 hard repetitions, and never treat the result as a reason to attempt an unsafe maximum.