Gas Mileage Calculator
The Gas Mileage Calculator computes gas mileage from the relation mpg = miles driven / gallons used. It takes 2 inputs (miles driven in miles, gallons of fuel used in gallons) and returns the gas mileage. These calculators are for everyday drivers, rideshare and delivery operators, small fleet managers and home mechanics who want to plan the cost or range of a journey, compare one vehicle or driving habit against another for running cost, put a performance figure such as acceleration or engine output into usable terms, or check that a size or part suits the vehicle before money is spent. Enter your values below and the result updates instantly, and you can share a permalink that pre-fills the exact calculation. Keep every input in one measurement system before you calculate, since mixing miles with litres, US gallons with imperial gallons, or inches with millimetres will quietly skew the answer, and where a figure describes how your vehicle actually behaves, take it from your own recent records (odometer readings, fuel receipts, the numbers printed on the car itself) rather than the brochure. For example, with miles driven = 450 miles, gallons of fuel used = 15 gallons, the gas mileage works out to 30, and the worked example further down the page shows every step so you can follow the arithmetic and reproduce it by hand. The method is the standard form documented by US DOE fueleconomy.gov, and the figure above each result carries the date it was last verified. Where the result depends on how the vehicle is driven rather than on fixed numbers, as with fuel use, range and acceleration, expect the real figure to move with driving style, load, terrain, traffic, weather, tyre pressure and mechanical condition, and treat anything affecting fitment or safety, such as a change of tyre or wheel size, as something to confirm with the vehicle handbook or a qualified fitter before you commit.
With Miles driven = 450 miles, Gallons of fuel used = 15 gallons, the result is 30.
Applies to: any numeric inputs. Method source: US DOE fueleconomy.gov, checked 2026-06-23.
The formula
mpg = miles driven / gallons used
Worked example
With Miles driven = 450 miles, Gallons of fuel used = 15 gallons:
- mpg = miles / gallons
- mpg = 450 / 15 = 30.00
- Gas Mileage = 30
This worked example is one of the automated golden-value tests this calculator must pass before it can publish.
What this assumes
- Inputs are real numbers in the units shown.
- The result is the exact value of mpg = miles driven / gallons used; general information, not professional advice.
Frequently asked questions
What formula does this use?
mpg = miles driven / gallons used, the standard form documented by US DOE fueleconomy.gov.
Does the result ever change over time?
No. This is a pure formula with no external rate, so the same inputs always give the same result.
Official sources and verification
- Method: US DOE fueleconomy.gov, checked 2026-06-23.
Reviewed by the CalculatorHub team, edited by James Graham, 2026-06-23. See our methodology. General information, not professional advice.