WheelSignal

WheelSignal

Results printed from https://wheelsignal.com/mpg-calculator. Nominal estimates; see assumptions below.

MPG & fuel economy calculator

Work out your real fuel economy from fill-ups, then see it in US MPG, imperial MPG, L/100 km and km/L.

Fuel economy from fill-ups

Units
Fill-ups

Each row is one tank: the distance driven since the last full fill, and the fuel added to fill it again. Only the first row is required.

Unit: mi
Unit: gal
Unit: mi
Unit: gal
Unit: mi
Unit: gal
Unit: mi
Unit: gal
Unit: mi
Unit: gal
Unit: mi
Unit: gal

Unit choices are saved only if you tick the box, in this browser’s local storage. Measurements are never saved or sent anywhere. A shared link carries the inputs after the # in the address, which browsers don’t send to the server.

Results

Enter the distance and fuel for at least one fill-up, or press Try an example, then Calculate.

How to measure your fuel economy

  1. Fill the tank until the pump clicks off and reset the trip odometer.
  2. Drive as you normally would.
  3. Fill up again to the click, and note the fuel added and the trip distance.
  4. Enter each tank as a row. More tanks give a steadier average, because how “full” the tank is varies a little each time.

This is the method described by Kelley Blue Book and most owner’s manuals. To convert a single figure, enter any distance and the matching fuel, for example 100 km and 7 L for 7 L/100 km.

Worked example: why the average is weighted

Tank one: 100 miles on 5 US gallons (20 MPG). Tank two: 300 miles on 7.5 gallons (40 MPG). Averaging the two MPG figures gives 30, but the car actually covered 400 miles on 12.5 gallons, which is 32 MPG. The longer tank should count for more, and dividing total distance by total fuel does that automatically.

Fuel economy units compared

  • MPG (US): miles per US gallon (3.785411784 L). Higher is better.
  • MPG (imperial): miles per imperial gallon (4.54609 L), used in the UK. Higher is better.
  • L/100 km: litres used per 100 km, used in Europe, Canada and Australia. Lower is better.
  • km/L: kilometres per litre. Higher is better.

Consumption units (L/100 km, or fuel per 10,000 miles) make savings easier to compare than MPG. Read MPG vs L/100 km for the full explanation.

Formulas used

economy (per tank) = distance ÷ fuel added overall economy = total distance ÷ total fuel L/100 km = litres ÷ km × 100 MPG (US) = 235.2146 ÷ L/100 km MPG (imperial) = 282.4809 ÷ L/100 km km/L = 100 ÷ L/100 km

Frequently asked questions

How do I calculate MPG myself?

Fill the tank to full and reset the trip odometer. Drive normally, then fill to full again and note how much fuel went in. Divide the miles driven by the gallons added. Repeating over several tanks gives a more reliable figure.

Why not average the MPG of each tank?

Because tanks cover different distances. Averaging per-tank MPG gives a short tank the same weight as a long one. The correct overall figure is total distance divided by total fuel, which is what this calculator reports. It shows both so you can see the difference.

Is UK MPG the same as US MPG?

No. UK figures use the imperial gallon (4.546 litres); US figures use the US gallon (3.785 litres). The same car shows about 20% higher MPG in imperial units. Pick the gallon that matches your fuel receipts.

Why is my MPG lower than the official figure?

Official ratings come from standard laboratory test cycles. Real-world economy depends on speed, traffic, temperature, short trips, load, tyre pressure and driving style.

What is “fuel per 10,000 miles” for?

Fuel saved isn’t proportional to the MPG number. Expressing consumption as fuel used over a fixed distance makes two cars, or two driving styles, easy to compare. Our guide to fuel economy units explains why.

Last updated .