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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.

Last reviewed June 6, 2026Source note includedFree tool

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.

Driving cost estimates change with traffic, route, fuel price, MPG, parking, tolls, return trips, and vehicle wear. Treat the result as trip-planning math.

Quick answer

Fuel Economy Calculator: what it calculates

Fuel Economy Calculator calculates miles per gallon from miles driven, gallons used, gas price, and annual miles. The visible formula 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

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

  • Use this fuel economy calculator to turn miles driven, gallons used, gas price, and annual miles into MPG and fuel cost estimates.
  • Estimating trip, commute, parking, toll, and fuel costs before choosing a route, schedule, or budget.
  • Comparing driving scenarios with miles, MPG, fuel price, parking, tolls, and commute frequency visible.
  • Turning a one-off route or recurring commute into monthly or annual cost context.

Before relying on it

Check first

  • Using ideal MPG when traffic, weather, cargo, terrain, idling, or city driving changes real fuel use.
  • Forgetting parking, tolls, return trips, detours, vehicle wear, or weekly frequency when comparing options.
  • Mixing one-way and round-trip distances or daily and monthly assumptions in the same estimate.

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. Benchmark ranges are broad planning heuristics unless this page names a specific source for the range.

Under 20 MPG: Fuel-heavy.

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

20 - 35 MPG: Common range.

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

35+ MPG: Higher 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

Trip and commute calculators use the route, frequency, and cost assumptions entered. Real costs can change with fuel price, detours, driving conditions, toll rules, and parking fees.

Last reviewed

June 6, 2026

Cite this page

Toolkit Shelf. Fuel Economy Calculator. Last reviewed June 6, 2026. 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.

Why might the real-world result differ?

Match the result to the task type: shopping tools depend on the same unit and usable quantity, home-project tools depend on field measurements and waste, date/time tools depend on counting rules, and conversion tools depend on the unit system.

Should I round the result?

Round for readability after checking the formula and units. Keep more precision when the result feeds another calculation, and add a task-specific buffer only when shortage, waste, or timing risk matters.

Why might another calculator show a different output?

Different tools may use different rounding, assumptions, default rates, methods, formulas, or input timing. Compare the visible method and inputs before relying on the output.