Miles per gallon from a fill-up, and MPG converted to L/100 km and km/L
Estimates only, not financial advice. What you type stays on your device. Checked against sources on 1 Oct 2026.To measure your MPG, fill the tank, reset the trip meter, drive, then fill up again: miles driven divided by gallons added is the miles per gallon. 330 miles on 11 gallons is 30 MPG, which is 7.84 L/100 km or 12.75 km/L. The conversion uses the U.S. gallon of 3.785411784 litres and the mile of 1.609344 km, both exact by definition.
Fill the tank, reset the trip meter, drive, then fill up again.
Enter the "Distance since last fill" and the "Fuel to refill" from the pump.
Read MPG (U.S.), L/100 km and km/L for that tank.
Press the Use button under the figures to cost a trip at the economy you measured.
The cost of a drive comes down to three numbers: how far, how much fuel the car uses for that distance, and what the fuel costs. This calculator takes them in whichever units your car and your country use, and gives the trip cost, each person's share and the cost per mile and per kilometre. Round trip doubles the one-way distance: 150 miles there and back at 25 MPG, with gas at $3.40, uses 12 gallons and costs $40.80.
Units. Choose miles with MPG and a price per U.S. gallon, kilometres with litres per 100 km, or kilometres with km per litre. Switching converts the figures already entered, so the trip stays the same trip. The conversions use the U.S. gallon of 231 cubic inches (3.785411784 litres) and the mile of 1.609344 km, both exact definitions in NIST Handbook 44. A UK MPG figure uses the larger Imperial gallon and is about 20% higher than the U.S. figure for the same car, so convert it to L/100 km before entering it.
MPG from a fill-up. Fill the tank, reset the trip meter, drive, and fill again: the distance divided by the fuel added is your real-world economy. Enter both and the page shows it as MPG, L/100 km and km/L, ready to use for the trip.
The rest of the article, and all 6 questions about Fuel Cost Calculator, are on the Fuel Cost Calculator page.
Divide the distance by the car's miles per gallon to get the gallons used, then multiply by the price per gallon. A 300-mile drive at 30 MPG needs 10 gallons, and at $3.50 a gallon that is $35.00. Double it for a round trip, and divide by the number of people sharing the cost.
Divide 235.215 by the MPG figure. The constant is 100 times the litres in a U.S. gallon (3.785411784) divided by the kilometres in a mile (1.609344). So 30 MPG is 7.84 L/100 km and 25 MPG is 9.41 L/100 km. The same division works the other way, from L/100 km back to MPG.
Fill the tank to the top and reset the trip meter. Drive normally, then fill up again and note the gallons added. Miles driven divided by gallons added is the real MPG: 330 miles on 11 gallons is 30 MPG. Averaging several tanks gives a steadier figure than a single one.
No. A UK figure uses the Imperial gallon of about 4.546 litres, while the U.S. gallon is 3.785 litres, so the same car shows roughly 20% more miles per gallon in the UK. Enter a UK figure as L/100 km instead: divide 282.48 by the UK MPG to convert it.
Rates and rules change; check the source before you rely on a figure.
Still stuck? Ask about Fuel Cost Calculator and anybody who knows can answer. No account needed.
On the related tools: Step-up SIP Calculator – See how raising your SIP every year changes the final corpus · GST Inclusive Calculator – Split a price that already includes GST into value and tax.