About

Indoor cycling metrics often rely on generic "Cycling" estimates which fail to account for the specific mechanical work performed. This calculator offers two modes of computation for higher fidelity. The Power Mode uses the laws of physics, converting the average wattage output directly into energy expenditure, adjusted for human mechanical efficiency (approximately 24%). This is the gold standard for cyclists using power meters or smart trainers.

For equipment lacking power data, the MET Mode utilizes Metabolic Equivalent of Task values derived from intensity descriptions. This provides a robust estimate based on perceived exertion and speed benchmarks specific to stationary ergometers.

Formulas

1. Power-based Calculation (Physics):

E_kcal ≈ P_avg × t × 3.64.184 × 0.24

Where P is Power in Watts, t is duration in hours, 0.24 represents 24% human gross mechanical efficiency, and 4.184 converts Joules to kcal.

2. MET-based Calculation:

Calories = MET × Weight_kg × Time_hr

Reference Data

Intensity Description	Avg Watts	MET Value
Very Light / Recovery	< 50W	3.0
Light Effort	50 - 100W	5.5
Moderate Effort	100 - 150W	7.0
Vigorous Effort	150 - 200W	10.5
Race Pace / High Intensity	> 200W	12.5

Frequently Asked Questions

Watts measure the actual mechanical work produced. Heart rate and speed can vary due to fatigue, hydration, or equipment calibration, but a Watt is a definitive unit of power ($1 \text{ J}/\text{s}$). Converting this work to calories with a known efficiency factor eliminates most estimation errors.

The human body is not 100% efficient; roughly 76% of energy burned is lost as heat, while ~24% is converted into mechanical movement (turning the pedals). This factor aligns with standard cycling physiology literature.