What is a good MPG rating?

For most passenger cars, 30+ MPG is considered good. Hybrids typically achieve 45–60 MPG, while large trucks or SUVs may get 15–20 MPG. City driving is usually 20–30% less efficient than highway driving.

How do I convert MPG to L/100km?

Divide 235.215 by the MPG value. For example, 30 MPG equals approximately 7.84 L/100km. This tool does the conversion automatically when you switch unit systems.

How do I measure fuel used accurately?

Fill your tank completely, reset your trip odometer, drive normally, then fill up again and note the exact liters or gallons added. That is the fuel used for the distance shown on the odometer.

Why does my calculated MPG differ from the manufacturer spec?

Manufacturer ratings are measured under controlled lab conditions. Real-world MPG is affected by driving style, road grade, load, tire pressure, air conditioning use, and fuel quality.

Does this tool work for liters and kilometers?

Yes. Select the Metric unit system to enter distance in kilometers and fuel in liters. The result is displayed as L/100km, the standard metric measure of fuel consumption.

Fuel Efficiency Calculator

Name: Fuel Efficiency Calculator
Availability: InStock
Author: Nham Vu

Enter distance and fuel used to calculate MPG or L/100km, and estimate the fuel cost for any trip.

Fuel Efficiency Calculator

Unit System

Distance Traveled

miles

Fuel Used

gallons

Optional — Trip Cost Estimate

Fuel Price

$ / gallon

Planned Trip Distance

miles

Enter distance and fuel used, then press Calculate.

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Summary

Enter distance and fuel used to calculate MPG or L/100km, and estimate the fuel cost for any trip.

How it works

Choose your unit system — Imperial (MPG) or Metric (L/100km).
Enter the distance you traveled and the amount of fuel you used.
The calculator instantly shows your fuel efficiency rating.
Optionally enter fuel price per unit and a trip distance.
The estimated fuel cost for that trip is displayed immediately.

Use cases

Track your car's fuel economy after every fill-up.
Compare efficiency before and after a tune-up or tire change.
Plan road-trip budgets by estimating total fuel cost.
Convert between MPG and L/100km for international comparisons.
Evaluate whether a newer, more fuel-efficient vehicle is worth buying.
Monitor fleet vehicles for unusual consumption spikes.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu