How to Calculate Fuel Cost per Km or Mile: Petrol, Diesel & Trip Examples
NextCodeHub Automotive Team
Cost Formula Quick Summary:
Cost per km ($/km) = Fuel Price per Liter ÷ Vehicle km/L
Cost per Mile ($/mile) = Fuel Price per Gallon ÷ Vehicle MPG
Why Knowing Your Fuel Cost per Km or Mile Matters
Whether you drive a daily commute to the office, work as a rideshare driver (Uber / Lyft), run deliveries, or split road trip expenses with friends, knowing your vehicle's exact cost of petrol per km or mile eliminates all budgeting guesswork.
Instead of guessing how much a journey will cost, you can calculate the exact cash expense down to the cent using simple formulas or our free fuel cost calculator.
How to Calculate Fuel Cost per Km (Formula & Example)
Depending on which metric efficiency unit your vehicle uses, here are the two formulas to work out fuel cost per kilometer:
Method A: Using km per Liter (km/L)
Cost per km = Petrol Price per Liter ÷ km/L
Example: Petrol is $1.50 per liter, and your car averages 15 km/L:
$1.50 ÷ 15 = $0.10 per kilometer
Method B: Using Liters per 100km (L/100km)
Cost per km = (L/100km × Price per Liter) ÷ 100
Example: Your car consumes 7.5 L/100km, and petrol costs $1.60/L:
(7.5 × $1.60) ÷ 100 = $12.00 ÷ 100 = $0.12 per kilometer
How to Calculate Fuel Cost per Mile (Formula & Example)
In the United States and UK, calculating your petrol or gas cost per mile is direct:
Cost per Mile = Fuel Price per Gallon ÷ Vehicle Combined MPG
Example: Regular gasoline costs $3.60/gallon, and your car gets 30 MPG:
$3.60 ÷ 30 = $0.12 per mile (12.0 cents/mile)
Short Trip Examples: How Much Does 10 & 40 Miles of Petrol Cost?
Drivers frequently ask: "How much does a quick 10-mile or 40-mile journey actually cost in petrol?" Here is the exact cost breakdown at an average gas price of $3.50 per gallon:
| Vehicle Category | MPG Rating | Cost per Mile | 10 Miles Petrol Cost | 40 Miles Petrol Cost |
|---|---|---|---|---|
| Hybrid Sedan (Prius) | 52 MPG | $0.067 | $0.67 | $2.69 |
| Compact Car (Civic) | 35 MPG | $0.100 | $1.00 | $4.00 |
| Midsize Sedan (Camry) | 30 MPG | $0.117 | $1.17 | $4.67 |
| Crossover SUV (CR-V) | 25 MPG | $0.140 | $1.40 | $5.60 |
| Large SUV / Truck (F-150) | 18 MPG | $0.194 | $1.94 | $7.78 |
Diesel Cost Per Kilometer vs. Petrol
Diesel vehicles achieve roughly 20% to 30% higher mileage in km/L due to the higher thermodynamic efficiency of compression-ignition engines. Here is how diesel cost per kilometer compares in practice:
- Petrol Car (14 km/L at $1.50/L): $1.50 ÷ 14 = $0.107 per km.
- Diesel Car (18 km/L at $1.65/L): $1.65 ÷ 18 = $0.092 per km.
Even though diesel fuel is $0.15 more expensive per liter in this example, the superior mileage results in a lower running cost per kilometer!
Calculate Your Exact Journey Cost
Ready to calculate the exact cost for your next trip? Use our free tools:
- Fuel Cost Calculator — Computes cost per km, cost per mile, and total trip expenses.
- Fuel Expense Calculator — Plan weekly and monthly fuel budgets.
- Gas Price Calculator — See how price fluctuations affect your wallet.
Frequently Asked Questions
How do you work out the cost of petrol per km?
To work out petrol cost per km, divide the price per liter by your vehicle's fuel efficiency in km/L: Cost per km = Fuel Price per Liter ÷ km/L. Alternatively, if your car is rated in L/100km: Cost per km = (L/100km × Price per Liter) ÷ 100.
How do you work out the cost of petrol per mile?
To calculate petrol cost per mile, divide the fuel price per gallon by your car's MPG: Cost per Mile = Price per Gallon ÷ MPG. For example, at $3.50 per gallon and 30 MPG: $3.50 ÷ 30 = $0.117 (11.7 cents) per mile.
How much does 10 miles of petrol cost?
At an average gas price of $3.50 per gallon: In a 30 MPG car, 10 miles costs $1.17 (10 ÷ 30 × $3.50). In a 20 MPG SUV, 10 miles costs $1.75. In a 50 MPG hybrid, 10 miles costs $0.70.
How much does 40 miles of petrol cost?
At $3.50 per gallon: In a 30 MPG car, 40 miles of petrol costs $4.67 (40 ÷ 30 × $3.50). In a 20 MPG vehicle, 40 miles costs $7.00. In a 50 MPG hybrid, 40 miles costs $2.80.
Is diesel cost per kilometer cheaper than petrol?
Diesel engines achieve 15–25% higher mileage per liter, which reduces the liters needed per km. However, whether diesel is cheaper per km depends on regional fuel price spreads: if diesel costs more than 15% above petrol, the running cost per km is roughly equivalent.