1RM Leg Extension Calculator
The Leg Extension 1RM Calculator helps you estimate the maximum weight you can lift on the leg extension machine for one repetition. Testing a true one rep max on leg extensions can be unsafe for your knees, so this calculator uses your working weight and reps to provide a safe, accurate estimate. After you calculate, our AI Personalized Coach will appear with training tips to improve quad strength while keeping your joints healthy.
How to Use the Leg Extension 1RM Calculator
Enter the weight you lifted on the leg extension machine.
Enter the number of reps you performed.
Hit “Calculate” to see your estimated 1RM.
Get tips from your AI Coach in the results area.
Why Use a Leg Extension 1RM Calculator?
- Track quad progress: Measure strength gains over time.
- Protect your knees: Avoid the risks of testing a true max directly.
- Optimize training: Set the right loads for hypertrophy, endurance, or strength.
- Balance your legs: Compare quad strength (leg extension) to hamstring strength (leg curl) for joint health.
Leg Extension vs Squat Strength Ratio
How strong should my leg extension be compared to my squat?
Most lifters can extend about 60-80% of their squat 1RM. For example, if you squat 120 kg, your leg extension 1RM may fall between 70-95 kg.
The squat engages your glutes, hamstrings, and core, while the leg extension isolates only the quadriceps. That is why the squat number will always be higher.
So, use leg extensions to strengthen quads, but don’t rely on them alone. Combine them with squats and lunges for balanced lower body strength.
Safety Tips for Heavy Leg Extensions
- Don’t kick the weight up explosively and control every rep.
- Stop short of full knee lockout to protect your joints.
- Warm up properly before heavy sets.
- Use a weight you can control with strict form.
- Avoid extremely heavy singles on the leg extension machine.