If a vehicle uses a known amount of fuel over one distance, how much will it use over another? Enter the known trip below to see the proportion and each calculation step.
Enter the known distance, fuel used and new distance.
Worked example: 150 miles on 6 gallons
First find fuel economy: 150 ÷ 6 = 25 miles per gallon. For 300 miles, divide 300 by 25 to get 12 gallons. The direct proportion gives the same answer: 6 × 300 ÷ 150 = 12.
Worked example: 252 miles on 7 gallons
The fuel economy is 252 ÷ 7 = 36 MPG. A 540-mile trip at that rate uses 540 ÷ 36 = 15 gallons. Keep intermediate values unrounded, then round the final answer to the precision the question requests.
Common mistakes
Dividing gallons by miles gives gallons per mile, not miles per gallon. Both work if you use the matching formula.
If the new distance is longer, fuel use should be higher under the same assumptions.
Keep units consistent. Do not mix kilometers with miles or US gallons with imperial gallons.
This calculates fuel consumed. Fuel already in the tank changes how much you need to buy.
Using liters and kilometers
The same proportion works when both distances use kilometers and fuel uses liters. For example, 8 liters over 100 kilometers means 20 liters over 250 kilometers. The interactive form above labels its inputs in miles and US gallons.