How to Calculate Fuel Cost for Any Trip (Petrol, Diesel & CNG)
Planning a road trip and wondering how much you will spend on fuel? Or just trying to track your monthly petrol expenses? Calculating fuel cost is simple once you know the formula — and this guide will show you exactly how to do it for petrol, diesel, or CNG vehicles, in km or miles.
Use our free Fuel Cost Calculator for instant results.
The Fuel Cost Formula
Fuel Cost = (Distance ÷ Fuel Efficiency) × Price per Litre
Where:
- Distance is your trip length in kilometres
- Fuel Efficiency is your vehicle’s mileage in km per litre (km/L)
- Price per Litre is the current fuel price in your city
This gives you the total cost in rupees for the trip.
Step-by-Step Example
Scenario: Mumbai to Pune (approximately 150 km), in a car with 15 km/L mileage, petrol at ₹104/litre.
Step 1 — Calculate litres needed: 150 km ÷ 15 km/L = 10 litres
Step 2 — Calculate cost: 10 litres × ₹104 = ₹1,040 one-way
For a round trip: ₹1,040 × 2 = ₹2,080 total
How to Calculate Fuel Cost for 500 km
This is one of the most searched questions. Here’s the calculation for a 500 km trip:
Fuel required = 500 ÷ Your car’s km/L
| Mileage (km/L) | Litres for 500 km | Cost at ₹103/L |
|---|---|---|
| 10 km/L | 50 litres | ₹5,150 |
| 15 km/L | 33.3 litres | ₹3,432 |
| 20 km/L | 25 litres | ₹2,575 |
| 25 km/L | 20 litres | ₹2,060 |
| 40 km/L (bike) | 12.5 litres | ₹1,288 |
How to Calculate Cost Per Kilometre
Cost per km = Fuel Price per Litre ÷ Fuel Efficiency (km/L)
Example: Petrol at ₹104/L, car doing 15 km/L: ₹104 ÷ 15 = ₹6.93 per km
This is an incredibly useful number. Once you know your cost per km, you can calculate the fuel expense for any distance instantly:
- 200 km trip: 200 × ₹6.93 = ₹1,386
- 1,000 km trip: 1,000 × ₹6.93 = ₹6,930
How to Calculate Km Per Litre (Finding Your Real Mileage)
Manufacturers quote ARAI figures, but your real-world mileage is often different. Here is how to measure it accurately:
- Fill your tank completely. Reset the trip meter to zero.
- Drive normally — a mix of highway and city is ideal.
- Fill up completely again. Note the litres added and the km on the trip meter.
- Divide: km ÷ litres filled = your real km/L.
Example: You drove 420 km and refilled 31 litres. 420 ÷ 31 = 13.5 km/L (real-world mileage)
Always use your actual mileage in the fuel cost formula, not the ARAI figure. Real-world mileage is typically 15–20% lower than ARAI for city driving.
How to Calculate Petrol Usage Per 100 km (L/100km)
Some European calculators use litres per 100 km instead of km per litre. To convert:
L/100km = 100 ÷ km/L
If your car does 15 km/L: 100 ÷ 15 = 6.67 L/100km
Diesel vs. Petrol: Cost Comparison
Diesel is usually cheaper per litre but not all vehicles run on it. Here is how to compare:
Petrol car: 15 km/L, petrol at ₹104/L → ₹6.93/km Diesel car: 18 km/L, diesel at ₹91/L → ₹5.06/km
The diesel car costs ₹1.87 less per km — which adds up to significant savings on long drives, but the diesel vehicle typically costs ₹1–2 lakh more upfront.
CNG Cost Calculation
CNG is measured in kg, not litres. The formula is the same but uses km/kg and price per kg:
Fuel Cost = (Distance ÷ km per kg of CNG) × Price per kg
A typical CNG car does 25–30 km/kg. At ₹90/kg:
- 500 km ÷ 25 km/kg = 20 kg CNG
- 20 × ₹90 = ₹1,800 (vs ₹3,432 for petrol)
CNG is significantly cheaper but requires proximity to CNG stations — a key consideration for long road trips.
How to Calculate Fuel Cost for a Fleet
For a fleet of vehicles making regular runs, the formula scales linearly:
Monthly Fleet Fuel Cost = Σ (Distance_i ÷ Mileage_i × Fuel Price)
Where i represents each vehicle. Most fleet managers track this as cost per km per vehicle and aggregate it. Our Fuel Cost Calculator handles individual vehicles; for fleet tracking, spreadsheets are typically used.
Tips to Reduce Your Fuel Cost
- Maintain tyre pressure. Under-inflated tyres increase rolling resistance and cut mileage by up to 3%.
- Avoid sudden acceleration. Smooth, gradual acceleration uses significantly less fuel than sharp bursts.
- Turn off AC at low speeds. AC can reduce city mileage by up to 20% in stop-and-go traffic.
- Maintain the engine. A clean air filter and fresh engine oil improve fuel efficiency measurably.
- Combine trips. Cold engines use more fuel — combining multiple errands into one trip saves fuel.
- Avoid idling. Idling for more than 30 seconds burns more fuel than restarting the engine.
Fuel Price Tracking in India
Petrol and diesel prices in India change daily based on international crude prices and state tax rates. Always check the current price in your city before planning a long trip. The major OMCs (IOCL, BPCL, HPCL) update prices at 6 AM daily.
As of mid-2024, prices typically ranged from:
- Petrol: ₹94 to ₹108/L depending on city
- Diesel: ₹87 to ₹96/L depending on city
- CNG: ₹75 to ₹95/kg depending on city
Use our Fuel Cost Calculator with today’s actual price from your city for accurate trip budgeting.