Fuel Efficiency Calculator

Fuel efficiency calculator results are most useful when the distance and fuel amount cover the same full-tank interval. Enter both values below to compare four common economy units and estimate fuel costs.

What This Calculation Shows

• Choose miles or kilometers for distance.
• Choose liters, US gallons, or Imperial gallons for fuel.
• See US MPG, Imperial MPG, L/100 km, and km/L together.
• Add the price per selected fuel unit to estimate total and distance-based costs.

One fill-up can be affected by traffic, weather, and pump shutoff. Average several full-tank results before judging a change in your vehicle.

Measure a Full-Tank Interval

Start with a full tank and record the odometer or reset the trip meter. Drive until at least half the tank is used, refill it, and record the fuel added. Use the miles or kilometers driven since the first fill. The EPA recommends using the same pump and nozzle when possible, stopping at the first automatic shutoff, and averaging two or three tanks for a better estimate. See the EPA's fill-up method for measuring fuel economy.

US MPG and Imperial MPG Are Different

A US gallon equals about 3.785 liters, while an Imperial gallon equals about 4.546 liters. The same trip therefore produces a higher Imperial MPG number. The calculator shows both and uses the official NIST volume conversion factors.

Use the Result to Spot a Change

Compare several tanks from similar driving, not one isolated result. A lasting drop can come from low tire pressure, a change in routes, heavy loads, cold weather, or a vehicle problem. Check the tire-pressure label, warning lights, and normal maintenance items before assuming one part has failed. The US Department of Energy explains how maintenance and tire pressure affect fuel use.

Reduce Fuel Use Without Guessing

Smooth acceleration, steady speeds, fewer short cold-engine trips, and less unnecessary cargo can reduce fuel use. Combine nearby errands when practical and track the next few full tanks to see whether a change actually helps. Review the government's fuel-saving driving guidance for more ways to cut consumption.