How to Calculate Fuel Cost Per KM – Formula for Petrol & Diesel
Petrol prices in India fluctuate frequently and vary by state. Knowing exactly how much your vehicle costs per kilometre — and how to calculate your fuel expense per trip — is essential for budgeting commutes, road trips, and business travel. This guide covers everything with practical Indian examples.
Why Calculate Fuel Cost Per KM?
Fuel cost per km is the most useful metric for vehicle running cost analysis. It lets you compare petrol vs CNG vs electric vehicles on a like-for-like basis, decide whether to drive or take public transport, plan accurate road trip budgets, and track changes in your vehicle's efficiency over time (a drop in km/litre is often the first sign of engine trouble).
Formula: Fuel Cost Per KM
Or equivalently:
Fuel Cost Per KM = Total Fuel Cost / Total Distance (km)
Step-by-Step: Calculate Your Fuel Cost Per KM
Method 1 (using mileage): Your car gets 16 km/l. Petrol = ₹106/litre.
- Fuel Cost Per KM = ₹106 / 16 = ₹6.625/km
- Monthly commute: 1,500 km/month
- Monthly Fuel Cost = 1,500 × ₹6.625 = ₹9,938/month
Method 2 (fill tank method — most accurate):
- Fill full tank. Set trip meter to zero.
- Drive normally until low fuel. Fill tank again. Note litres refuelled and km driven.
- Mileage = km driven / litres refuelled
- Cost/km = Fuel price / Mileage
Petrol vs Diesel vs CNG Comparison
| Fuel | Approx Price | Avg Mileage | Cost/KM |
|---|---|---|---|
| Petrol (Car) | ₹106/L | 14 km/l | ₹7.57 |
| Diesel (Car) | ₹93/L | 18 km/l | ₹5.17 |
| CNG (Car) | ₹90/kg | 22 km/kg | ₹4.09 |
| Electric | ₹8/unit | 6-8 km/unit | ₹1-1.33 |
How to Reduce Fuel Cost Per KM
- Maintain optimal tyre pressure (saves 3-5% fuel)
- Drive at 70-80 km/h on highways (optimal engine efficiency zone)
- Avoid unnecessary idling — switch off engine if waiting more than 1 minute
- Service air filter every 15,000 km (dirty filter increases fuel consumption by 10-15%)
- Reduce AC usage in slow city traffic (use blower + windows instead)
- Plan routes to avoid traffic-heavy timings
Frequently Asked Questions
What is a good fuel efficiency for Indian conditions?
For petrol cars in city conditions: 12-15 km/l is typical. On highways: 15-18 km/l. Economy cars (Alto, WagonR) can achieve 18-22 km/l. SUVs typically give 10-14 km/l.
Does fuel consumption increase in city traffic vs highway?
Yes. Stop-and-go traffic, idling, frequent braking, and constant acceleration in cities reduce mileage by 20-40% compared to steady highway driving.
🔢 Plan your trip: Use our Fuel Cost Calculator, Fuel Cost Per Trip Calculator, and Fuel Consumption (km/l) Calculator.
Try it yourself — Free & Instant
No signup required. Results in seconds.
Open Fuel Cost Calculator →