Free calculator
MPG Comparison Calculator
Compare annual fuel use and cost for two vehicles.
Formula annual miles ÷ MPG × fuel price
Compare fuel savings between two MPG ratings
This calculator holds annual miles and fuel price constant while comparing two fuel-economy figures. It subtracts the comparison vehicle's annual fuel cost from the current vehicle's annual fuel cost. A positive result is a saving; a negative result means higher fuel spending.
Worked example
At 12,000 miles and $3.50 per gallon, a 25-mpg vehicle uses $1,680 of fuel per year. A 35-mpg vehicle uses $1,200. The difference is $480 per year, or $40 per month.
How to use the result
Fuel savings alone do not establish whether buying another vehicle is economical. Compare the saving with the purchase-price difference and other ownership costs. If the vehicles use different fuel grades, calculate each annual fuel cost separately with its own price.
Sources and assumptions
U.S. EIA public gasoline price table Accessed 2026-09-05Calculation methodology. Worked examples use the expressly stated inputs; sample prices are illustrative rather than local quotes.
Use a vehicle service sheet next
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Frequently asked questions
How much money does a higher MPG save?
Calculate annual miles divided by each MPG rating, multiply both by fuel price, then subtract the two annual costs. The saving depends on all three inputs, not just the MPG difference.
Why is the saving negative?
The comparison MPG is lower than the current MPG, so the comparison vehicle uses more fuel for the same mileage and price.
Can I compare regular and premium fuel costs here?
This tool uses one fuel price for both vehicles. Use the annual fuel cost tool separately for each vehicle when their fuel prices differ.
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