Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
MPG
29.09
km / L
12.37
L / 100 km
8.09
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter distance (miles).
- 2Enter fuel used (gallons).
- 3Read your mpg on the right — it updates as you type.
- 4Hit Share to keep the scenario or send it to someone.
About this calculator
Compute vehicle efficiency in MPG (miles per gallon) and L/100km from distance traveled and fuel consumed.
Worked example
Using the values the calculator loads with:
Inputs
- Distance (miles): 320
- Fuel used (gallons): 11
Results
- MPG: 29.09
- km / L: 12.37
- L / 100 km: 8.09
What each field means
Inputs
- Distance (miles)
- The distance (miles) used in the calculation. Starts at 320 so you have a working example on load.
- Fuel used (gallons)
- The fuel used (gallons) used in the calculation. Starts at 11 so you have a working example on load.
Results
- MPG
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- km / L
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- L / 100 km
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the gas mileage calculator work?
Compute vehicle efficiency in MPG (miles per gallon) and L/100km from distance traveled and fuel consumed.
What do I need to enter?
2 values: distance (miles), and fuel used (gallons). Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the mpg result mean?
It is returned as a decimal number and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Estimates assume standard, average conditions — local rules, pricing, and materials vary.
Who is this tool for?
It's built for anyone doing everyday planning maths — a quick estimate that would otherwise need four browser tabs and a calculator app.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Gas Mileage Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/gas-mileage
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/gas-mileage" target="_blank" rel="noopener">Gas Mileage Calculator — RevenueLab</a> (2026).</p>
Source: [Gas Mileage Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/gas-mileage) (2026).