⛽ Fuel Cost Calculator

Fuel Cost Calculator - Petrol, Diesel, CNG and EV Running Costs Compared

Fuel is often the largest variable cost of owning a vehicle - yet most people have only a rough sense of what they spend. Knowing your exact cost per kilometre, monthly commute expense, and how those numbers compare across fuel types makes a real difference when choosing a vehicle, evaluating a switch to CNG or EV, or planning a long trip. This calculator makes those numbers precise.

Fuel Cost Formula - How the Calculation Works

The core formula is simple: Fuel Cost = (Distance ÷ Mileage) × Fuel Price.

Distance ÷ Mileage gives you the fuel consumed (litres or kg). Multiplying by the price gives the total cost. For monthly commutes: multiply your daily one-way distance by 2 (round trip) and by the number of working days. Cost per km = Total Cost ÷ Distance.

For EVs, the unit changes from litres to kWh (kilowatt-hours) and mileage becomes km/kWh (energy efficiency). The formula structure is identical: (Distance ÷ km/kWh) × ₹/kWh.

Running Cost Comparison - Petrol vs Diesel vs CNG vs EV

Why Your Real Mileage Is Lower Than ARAI Figures

The certified mileage (ARAI in India, EPA in the US, WLTP in Europe) is tested in controlled laboratory conditions: constant temperature, no air conditioning, smooth acceleration, flat test track, and a lighter test weight. Real-world driving is very different:

• Air conditioning: Reduces mileage by 15–20% in city driving. Compressor load is significant at low speeds.
• City stop-start traffic: Reduces mileage 30–40% vs highway. Engines are less efficient at low speeds and during frequent acceleration from rest.
• High highway speeds: Above 80 km/h, aerodynamic drag increases significantly. Mileage drops 10–15% between 80 and 100 km/h, and another 15% between 100 and 120 km/h.
• Tyre pressure: Under-inflated tyres increase rolling resistance. Maintaining recommended pressure improves mileage 3–5%.
• Vehicle load: Extra passengers and luggage increase fuel consumption. Every 100 kg of extra load reduces mileage approximately 5%.

As a practical rule, expect real-world mileage to be 20–25% below the ARAI figure for most cars. Use the Manual Entry option in this calculator to enter your actual observed mileage from past fill-ups for the most accurate cost estimate.

Is CNG Worth Switching to in India?

CNG makes financial sense for drivers with high monthly mileage. The key numbers to evaluate:

• Monthly savings: A driver doing 1,500 km/month saves approximately ₹3,000–5,000/month switching from petrol to CNG.
• CNG kit cost: Factory-fitted (Maruti, Hyundai CNG variants): ₹50,000–80,000 premium. Aftermarket retrofit: ₹15,000–25,000 (reduces warranty, insurance complexity).
• Payback period: At ₹4,000/month saving, a ₹60,000 kit pays back in 15 months.
• CNG is ideal for: city taxis, high-mileage commuters, delivery vehicles.
• Downsides: reduced boot space (CNG cylinder), range anxiety in cities with limited CNG stations, slight power reduction compared to petrol.