Gas Mileage Calculator
Use this free Gas Mileage Calculator to calculate your Fuel efficiency instantly and accurately.
Trip
Fuel economy
What is a Gas Mileage Calculator?
The Gas Mileage Calculator helps you calculate your vehicle’s fuel economy in MPG, L/100km, and km/L. Just enter your numbers and the tool does the rest — no manual math, no guesswork.
How to calculate Gas Mileage manually (the formula)
The specific formula depends on what you are calculating. The calculator applies the correct equation automatically, but understanding the formula helps you verify the results and adapt them to your own needs.
Example calculation
Enter your values into the calculator and it will produce an instant result. For a step-by-step walkthrough, try different inputs and observe how each one affects the outcome.
Common mistakes
- Using a partial tank — Always fill the tank completely and reset the trip meter for an accurate MPG reading.
- Mixing units (miles with litres) — Use miles and gallons for US MPG, or km and litres for metric. Mixing them gives wrong results.
- Trusting the car’s display blindly — Dashboard MPG estimates tend to be optimistic. Hand-calculate for true fuel economy.
Frequently asked questions
How do I calculate gas mileage?
Divide the miles driven by the gallons of fuel used. MPG = Miles ÷ Gallons. Fill the tank twice for an accurate reading.
What is a good MPG?
A good MPG depends on the vehicle. 25–30 MPG is typical for sedans, 15–20 MPG for trucks, and 40+ MPG for hybrids.
How do I calculate L/100km?
Convert miles to km (1 mile = 1.609 km) and gallons to litres (1 gal = 3.785 L). Then L/100km = (L ÷ km) × 100.
How accurate is the MPG calculation?
Hand-calculated MPG is more accurate than your car’s display. For best results, use multiple fill-ups.
What factors affect gas mileage?
Driving habits (speeding, idling), tire pressure, cargo weight, weather, and engine condition all affect MPG.
How do I improve my car’s fuel economy?
Maintain steady speeds, avoid hard acceleration, keep tires properly inflated, and remove excess weight from the vehicle.