Start with a full tank
Fill to the pump’s first automatic cut-off, then reset your trip counter or note your odometer reading. Don’t top up beyond the cut-off.
The fuel economy calculator
Know your MPG.
Understand every mile.
Turn your mileage and fuel receipt into a clearer picture of what your car uses—and what it costs to run.
Your fuel economy
Ready when you areMiles per gallon
—UK MPG
Based on an imperial gallon (4.54609 litres).
Miles per litre— mi/L
US MPG equivalent— MPG
Cost per mile—
Fuel consumption— L/100 km
Total fuel cost—
Cost per 100 miles—
Enter your distance and fuel used to get started. Add a fuel price to see your running costs too.
Free to use. No sign-up. Calculations run in your browser. Google advertising is enabled.
A better reading in three simple steps.
The full-tank methodLet your normal miles add up
Drive as you normally would. A longer distance gives a more representative reading than a short trip.
Keep the receipt. Do the maths.
Fill to the first cut-off again. Enter the distance driven and fuel quantity on this receipt using the matching units. That quantity approximates the fuel used between fills.
Simple inputs. Transparent maths.
Choose UK imperial gallons (4.54609 litres) or US liquid gallons (3.785411784 litres). Both MPG figures are displayed, alongside miles per litre. The same journey has a higher UK MPG figure because an imperial gallon is larger. Higher MPG means you travel further on the same amount of fuel; lower litres per 100 km means you use less.
UK MPG = miles × 4.54609 ÷ litres
US MPG = miles × 3.785411784 ÷ litres
Miles per litre = miles ÷ litres
Cost per mile / km = total fuel cost ÷ distance in that unit
Miles = kilometres ÷ 1.609344
L/100 km = litres × 100 ÷ (miles × 1.609344)
For example, 350 miles using 40 litres at £1.459 per litre works out at 39.8 UK MPG, £0.167 per mile and £58.36 in fuel.
A few useful answers
Which fuel and price units should I use?
UK mode accepts fuel quantity in litres; US mode accepts US liquid gallons. Independently choose GBP, USD or EUR and a price per litre, price per US gallon or total fuel cost. Enter pounds, dollars or euros—not pence or cents. For example, 145.9p per litre is entered as 1.459 with GBP selected. You can leave cost blank to calculate economy only.
What happens when I switch units?
Existing distance and fuel quantities are converted automatically. MPG and miles per litre always use miles, even when you enter kilometres. Cost per distance follows your selected miles or kilometres. The currency and price unit are independent of your UK/US setting. Changing currency keeps the entered amount and treats it as a price in the new currency; it does not convert exchange rates.
Does this work for petrol and diesel?
Yes. The maths works for either fuel, provided you select the units that match your distance and fuel quantity. It doesn’t calculate electric vehicle efficiency.
Why is my result different from my dashboard?
Dashboard figures are estimates and may cover a different period. Refuelling levels, driving conditions and rounding can also affect the comparison. Compare several full-tank readings for a more useful picture.
Does cost per mile include all running costs?
No. These results cover fuel only. Insurance, servicing, tyres, tax, finance and depreciation are not included. Cost per 100 miles or kilometres assumes the same fuel economy and fuel price.
Are my details saved?
The calculator code processes your entries on your device and does not save them in cookies or local storage. This page also loads Google AdSense, which may use cookies and process device, IP address and browsing information to serve and measure ads, subject to applicable consent choices. Learn how Google uses information from sites that use its services.