How we work it out
Litres per 100 km, times the price per litre, gives the cost per 100 km. Divide by 100 for a cost per kilometre, then multiply by how far you actually drive in a week to get a weekly and yearly figure. It's the same unit-cost logic our electricity calculator uses for appliances, just priced at the bowser instead of the meter.
Worked example: a typical car doing 8 L/100 km, driven 250 km a week, at the $1.80/L reference price: 8 L × $1.80 = $14.40 per 100 km, so about $36 a week or roughly $1,877 a year. The same driving in an EV charged at home, on the national average electricity rate, works out closer to $726 a year, using the same 16 kWh/100 km and 10% charging-loss basis our EV home charging calculator uses.
Why this number swings so much between cars
Fuel efficiency is the biggest lever here, and it varies a lot: a small hatchback can sit around 6 L/100 km while a large SUV or ute is often double that at 10 to 12 L/100 km, so two drivers covering the exact same distance can pay close to double for it. Mostly-city, stop-start driving also burns noticeably more than a highway-heavy commute, since a car uses the most fuel accelerating from a standstill. Your own trip computer's average, if your car has one, is a more honest number than the sticker figure, which is measured under lab conditions.
Common questions
How do I find my car's fuel efficiency?
Most cars built since the mid-2000s show a running average on the trip computer or dashboard display, usually in L/100 km. That real-world figure is more accurate for this calculator than the official lab-tested rating on the windscreen sticker, which tends to run a little optimistic against everyday driving.
Does this account for premium fuel?
Not directly. Set the price per litre field to whatever grade you actually buy, since 91, 95 and 98 octane all price differently at the bowser, and premium-only engines usually require the higher grade regardless of price.
Is an EV really cheaper to run than a petrol car?
On current reference prices, yes, usually by a wide margin, since electricity per kilometre is typically a third or less of the price of petrol. See our EV home charging cost calculator for the full comparison, including public fast charging.
Sources
Electricity rates: AER Default Market Offer (NSW, SA, south-east QLD), Victorian Default Offer, and each remaining state's regulated tariff, current for 2026–27. Appliance figures: the energyrating.gov.au registration database (July 2026 snapshot). Methods and assumptions are described on each page.