Leg Extension Calorie Calculator (Calories by Reps or Time)

Estimate calories burned on the leg extension machine from your body weight and workout time, using a standard MET value for resistance training.

Solve for

Gross energy includes resting expenditure; net energy subtracts the standard 1-MET resting estimate.

Estimates only. METs describe general resistance training. The mechanical model needs effective load and vertical load travel; machine pad travel may differ. Neither method measures your personal calorie burn.

Body weight

Average effort (MET)

3.5: general resistance training, multiple exercises; 6: vigorous resistance training. No leg-extension-specific value is established here.

Session duration (minutes)

Leg Extension Energy Models

The session model uses gross kcal = MET × 3.5 × body weight (kg) ÷ 200 × minutes. Net energy uses MET minus 1. The 2024 Adult Compendium lists 3.5 MET for multiple resistance exercises and 6 MET for vigorous resistance training; neither is a leg-extension-specific measurement. The separate mechanical model below retains an editable 18-inch vertical-load-rise assumption.

E = m \times 9.80665 \times d \times R / 4184 / (η / 100) \times (1 + a / 100)

Use effective moving mass and its vertical rise, accounting for the machine mechanism. An ankle-pad arc or the number printed on a weight stack may not describe the actual load-motion product. Efficiency and lowering allowance are explicit editable assumptions; blank values use 20% and 10%. This model excludes rest, setup and other body movement.

At η = 20% and a = 10%: E \approx W \times R \times D \times 0.001782265

E = modeled metabolic energy (kcal), not measured whole-session calories
m = effective moving mass (kg); W = its equivalent in pounds
R = total repetitions; η = assumed positive-work efficiency (%); a = extra lowering energy (%)
d = vertical load rise (m); D = the same rise in feet

Example: 100 lb effective load, 10 repetitions and 18 inches vertical rise at the stated 20%/10% assumptions give approximately 2.67 kcal in the mechanical model. Do not add this to the separate MET session estimate.

Mechanical Model Energy Per 10 Reps

Loaded Weight	Model kcal for 10 Reps	Model kcal per Rep
50 lb	1.34	0.134
100 lb	2.67	0.267
150 lb	4.01	0.401
200 lb	5.35	0.535

What Is a Leg Extension?

The leg extension is a machine-based isolation exercise that trains knee extension. It primarily targets the quadriceps, especially the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.

Leg Extension Quick Facts

Main muscle group: quadriceps
Primary joint action: knee extension
Common training ranges: 10 to 15 reps for moderate sets, 15 to 20 reps for lighter burn sets
At fixed assumptions, effective load, repetition count and vertical load rise increase mechanical model energy; this does not establish actual total calorie burn
MET session estimates apply an average activity rate; mechanical estimates require the machine load-motion relationship

How to Use the Calculator

Choose session calories, a mechanical load model, a comparison, or a target-time/repetition solve.
Enter the fields shown for that method. For a mechanical model, use effective load and vertical load rise; sets and repetitions are whole numbers.
Review the assumptions, then select Calculate. Open Calculation details for formulas. Target time and repetitions are model results, not workout recommendations.