Toolkit Shelf

Everyday Calculators

Fuel Economy Calculator

Use this fuel economy calculator to turn miles driven, gallons used, gas price, and annual miles into MPG and fuel cost estimates.

Reviewed May 25, 2026EstimateFormula shown

Quick answer

Fuel Economy Calculator: what it calculates

Fuel Economy Calculator calculates miles per gallon from miles driven, gallons used and gas price. The core method is MPG = miles driven / gallons used; gallons per 100 miles = gallons used / miles driven x 100.

ResultMiles per gallon
InputsMiles driven, Gallons used, Gas price, Annual miles
FormulaFuel economy formula

Live calculator

Fuel economy

Miles per gallon30.95 MPG

Miles driven divided by gallons used.

Gallons per 100 miles3.23 gal

A lower gallons-per-100-miles number means less fuel used for the same distance.

Fuel cost per mile$0.118

Based on $3.65 per gallon.

Annual fuel cost$1,415.08

12,000 miles at the calculated fuel economy.

Formula

Fuel economy formula

MPG = miles driven / gallons used; gallons per 100 miles = gallons used / miles driven x 100

The fuel cost estimate multiplies fuel used by gas price and assumes the same MPG across the annual miles entered.

How to use

Steps

  1. Enter miles driven since a fill-up or for a measured trip.
  2. Enter gallons used for that same distance.
  3. Add gas price to estimate cost per mile.
  4. Use annual miles to estimate yearly fuel cost at that MPG.

Example

Sample calculation

Miles driven325
Gallons used10.5
Fuel economy30.95 MPG
Cost per mile$0.118

Calculator use

Best for

  • Quick miles per gallon from miles driven, gallons used and gas price.
  • Quick everyday math with the result and formula in one place.
  • Shopping, date, time, unit, school, or household comparisons.
  • A fast check before moving the numbers into a spreadsheet.

Before relying on it

Check first

  • Entering miles driven, gallons used and gas price from different time periods or scenarios.
  • Mixing units, dates, or original values across the same calculation.
  • Rounding early and then using the rounded number in another step.
  • Copying a result without checking whether the inputs match the real-world question.

Details

What to know before using the result

These notes make the assumptions explicit, especially where the same search query can mean slightly different things.

Measurement windowSame tank or trip

Use miles and gallons from the same driving period. Mixing a trip distance with a different fuel purchase will distort MPG.

Gallons per 100 milesConsumption view

Gallons per 100 miles can make fuel use easier to compare because lower numbers always mean less fuel burned.

Real-world variationDriving conditions matter

Speed, weather, traffic, tire pressure, terrain, cargo, and driving style can move real MPG away from sticker estimates.

Source notes

References used for this calculator

U.S. Environmental Protection AgencyExplains vehicle fuel economy labels and official fuel economy information.U.S. Department of EnergyProvides fuel economy guidance and notes factors that affect gas mileage and fuel cost.

Benchmarks

How to read the result

The calculator is a decision aid, not a fixed rule. Use the output to compare scenarios and document your assumptions.

Under 20 MPGFuel-heavy

Annual fuel cost becomes sensitive to gas price and miles driven.

20 - 35 MPGCommon range

Useful baseline for many gasoline cars, SUVs, and trucks.

35+ MPGHigher efficiency

Lower fuel use can matter most for high-mileage drivers.

Calculator accuracy

Methodology and assumptions

The formula, inputs, example, and limitations are shown so the result is checkable, not just a number in a box.

Formula

MPG = miles driven / gallons used; gallons per 100 miles = gallons used / miles driven x 100

Inputs used

Miles driven, Gallons used, Gas price, Annual miles

Limitations

Results are estimates for quick planning and should be checked before important financial, legal, tax, health, or business decisions.

Last reviewed

May 25, 2026

Cite this page

Toolkit Shelf. Fuel Economy Calculator. Retrieved May 25, 2026, from https://toolkitshelf.com/tools/fuel-economy-calculator

FAQ

Common questions

How do I calculate MPG?

Divide miles driven by gallons used for the same trip or fill-up period.

Why show gallons per 100 miles?

Gallons per 100 miles shows fuel consumed for a fixed distance, which can make vehicle comparisons easier.

Is this the same as EPA-rated MPG?

No. This calculator estimates your observed MPG from miles and gallons. Official EPA estimates use standardized testing and label rules.