Fuel Consumption & MPG Calculator

How to calculate fuel consumption

1. Choose Calculate from fuel used, then enter the distance travelled and fuel consumed over that same interval.
2. Select kilometres or miles and litres, US liquid gallons or Imperial gallons. If you have odometer readings, enable that option instead of entering the distance.
3. Choose the result unit. The main answer updates when every active field is valid; the other equivalent units are available in Calculation details.
4. To convert an existing figure, choose Convert a fuel-economy figure and select its original unit. Copy the current result or Clear to start again.

What this calculator includes

• Average consumption from two measurements, with optional start and end odometer readings.
• Conversion between L/100 km, km/L, US MPG and Imperial MPG.
• Explicit US liquid and Imperial gallons, without guessing your units from the page language.
• One main result, with equivalent units and calculation notes kept in details.
• Browser-side calculation and a copyable summary of the active inputs and result.

When it is useful

• Work out a petrol or diesel vehicle's observed fuel consumption after a measured driving interval.
• Compare fuel-economy figures expressed in different units, while keeping US and Imperial gallons distinct.
• Find a consumption figure to use in the separate Trip Fuel Calculator when planning fuel quantity for a future journey.

Understanding your fuel-economy result

L/100 km measures fuel used per distance: divide litres by kilometres and multiply by 100. Km/L and MPG measure distance travelled per fuel volume. A lower L/100 km value and a higher km/L or MPG value each mean less fuel per distance, but they are different ways to express the same ratio.

For a refill-based measurement, start with a full tank and record the odometer. Do not include that first fill in the fuel used. Add up all later additions, including the final refill that restores a comparable full level, and record the ending odometer there. A partial refill alone does not establish the fuel consumed over the measured distance. Follow the vehicle and pump instructions and do not overfill.

When using an odometer, the travelled distance is the ending reading minus the starting reading. Both readings must use the same unit and the ending value must be larger. Resets, rollovers or readings from different odometers need a separately established distance.

One international mile is 1.609344 km. A US liquid gallon is 3.785411784 L; an Imperial gallon is 4.54609 L. MPG therefore needs its gallon definition. For a given journey, the numerical Imperial MPG value is higher than the US MPG value.

Conversions use the unrounded ratio, then round the displayed answer to 2 decimal places. When combining compatible measured intervals, divide total fuel by total distance; do not take a simple mean of L/100 km or MPG figures from trips of different lengths or fuel quantities.

This tool measures a past interval or converts a known figure. The separate Trip Fuel Calculator estimates fuel quantity from a distance and a consumption rate you already know. Actual future use can change with conditions, so neither number is a guaranteed tank range or an official test rating.

Fuel consumption and MPG examples

500 km with 35 L gives 7 L/100 km and about 14.29 km/L. The same interval is about 33.60 US MPG or 40.35 Imperial MPG.

300 miles with 10 US liquid gallons gives 30 US MPG, about 7.84 L/100 km and 36.03 Imperial MPG. Changing the gallon definition changes the input meaning; it is not just a different label.

A known figure of 20 km/L converts to 5 L/100 km. Starting and ending odometer readings of 12,000 km and 12,500 km with 35 L give the same 7 L/100 km result as entering 500 km directly.

What the result does not tell you

The measurements must cover the same interval. Refill accuracy, rounding and driving conditions affect the estimate; this page does not diagnose a vehicle or certify an EPA or WLTP rating.

For a plug-in hybrid, a liquid-fuel figure omits electric energy. Use the separate EV Energy Consumption Calculator for an appropriate distance and electric-energy measurement.

This tool does not provide live fuel prices, fuel cost, remaining range, emissions, route planning, vehicle-specific recommendations or a saved refill log.

Input amounts use up to 3 decimal places from 0.001 to 1,000,000. A starting odometer reading may be zero. Enter digits without thousands separators; input unit changes keep the number and reinterpret it in the selected unit.

Privacy and copying results

The calculation runs in your browser. This tool does not send or save your entered measurements and does not put them in the page URL.

Copy uses the current active inputs and includes their units, the selected answer, equivalent rates and qualifications. If browser copying is unavailable, a selectable text box lets you copy the same summary manually. Normal site requests and consent settings still apply.