Cycling Calorie Calculator

How accurate are cycling calorie estimates?

Power-based estimates (watts × time) are the most accurate available without metabolic testing, typically within 5–10%. Speed-based estimates using MET values are less accurate (15–25% error) because terrain, wind, and drafting dramatically affect the relationship between speed and effort. If you have a power meter, always use it.

What is the kJ ≈ kcal approximation in cycling?

A useful rule in cycling is that kilojoules (kJ) of work output roughly equals kilocalories (kcal) burned. This works because the human body is about 23–26% efficient — so to produce 1 kJ of mechanical work, it burns about 4.35 kJ of chemical energy (≈ 1 kcal ≈ 4.18 kJ). The approximation is never exact but is close enough for practical fuelling.

Does elevation affect calorie burn on the bike?

Yes, significantly. Climbing requires substantially more power than flat riding at the same speed. A 70 kg rider climbing 1,000m of elevation will burn approximately 400–500 extra kcal compared to the same time spent on flat road. If you have power data from a climb, use the power-based calculation for accurate results.

How much should I eat on long rides?

Research suggests cyclists can absorb 60–90g of carbohydrates per hour (up to 120g/hr with mixed carbohydrate sources). For rides over 90 minutes, aim to consume 30–60g of carbs per hour from gels, bars, or sports drinks. Total calorie intake during the ride should replace 50–70% of what you burn — you can't replace everything in real time.

Why does my Garmin show different calories than this calculator?

Garmin and other devices use proprietary algorithms combining heart rate, speed, power (if available), and personal data. The differences are usually due to varying efficiency assumptions. Power-based calculations (this tool's primary method) and Garmin's power-based estimates should be fairly close; heart-rate-based estimates can vary more widely.