Travel, Auto & Lifestyle
Gas Mileage Calculator
Gas Mileage Calculator is a browser-based calculator tool on CalcToolsBase. Free, browser-based gas mileage tool. Enter miles driven and US gallons used to get miles per gallon, plus km/L and L/100 km equivalents. To use it, enter your values and view the result directly in your browser — no signup and nothing to install.
Gas Mileage Calculator is a browser-based way to work out your fuel economy. Feed it your distance driven and fuel used and it computes your fuel economy in mpg, km/L and L/100km on the spot, keeping your data local.
Estimate only. Real fuel economy varies with vehicle load, traffic, terrain, driving style, tyre pressure, weather, and fuel type. Everything runs locally in your browser and nothing you enter is uploaded.
About this tool
With the Gas Mileage Calculator you can work out your fuel economy in a few seconds. Supply your distance driven and fuel used and read your fuel economy in mpg, km/L and L/100km, computed via distance ÷ fuel used. The tool is free, runs locally, and keeps every value on your machine.
How to use
- Note the miles driven for the trip or tank.
- Note the US gallons of fuel you used.
- Enter both numbers in the fields above.
- Press Calculate to see mpg with metric equivalents.
Why use the Gas Mileage Calculator
Instant
Each result is worked out on your device the moment you press Calculate.
Private
The numbers you enter stay in your browser and are never uploaded.
Free
No signup and no paywall to use any tool in this set.
Works offline
Once the page has loaded it keeps working on a weak or dropped connection.
Clear units
Inputs and outputs name their units so you know exactly what you are reading.
Honest by design
Uses simplified browser-side formulas for estimates; real fuel economy varies with driving conditions, load and how you measure fuel.
Common uses
Gas Mileage for comparing efficiency between fill-ups
Gas Mileage when comparing vehicles
Gas Mileage when reviewing a long trip's mileage
Gas Mileage for spotting an efficiency drop
Gas Mileage when tracking your fuel economy
Gas Mileage for a fuel-economy estimate
Technical notes
Gas Mileage Calculator divides distance travelled by fuel used to give fuel economy in mpg, km/L and L/100km.
Real fuel economy varies with load, traffic, terrain, driving style and conditions.
Nothing you type is uploaded — the calculation happens entirely on your device.
Worked example
Driving 400 km on 25 L gives 400 ÷ 25 = 16 km/L (or 6.25 L/100km).
FAQ
Can I calculate mpg and km per litre together?
Yes. The tool shows US miles per gallon first and also prints the km per litre and litres per 100 km equivalents from the same trip.
Should I enter US or imperial gallons?
Enter US gallons. A US gallon is about 3.785 litres; if you measured in litres, divide litres by 3.785 first.
What distance and fuel should I use?
Use the miles driven on one tank or trip and the gallons it took to refill, so the ratio reflects actual driving.
Why is my mpg lower than the sticker figure?
Quoted economy comes from standard tests. City traffic, cargo, weather, and driving style usually lower real mpg.