Last updated: July 16, 2026
Fuel Mileage Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
This fuel mileage calculator computes a vehicle's fuel efficiency from distance traveled and fuel consumed. It supports US miles/gallons, UK miles/imperial gallons, and metric km/liters inputs. Outputs include US MPG, UK MPG, km/L, L/100km, gallons-per-mile, total trip cost, and cost-per-distance-unit. The primary formula is MPG = Distance (miles) / Fuel (US gallons), with all other units derived from this base calculation.
Fuel mileage equals the distance you traveled divided by the amount of fuel you used. For example, if you drove 300 miles and used 10 gallons, your fuel mileage is 30 miles per gallon. In metric terms, divide kilometers by liters to get km/L, or divide 100 by km/L to get L per 100 km.
Key Takeaways
- Fuel mileage (MPG) is calculated by dividing distance traveled by fuel consumed - higher MPG means better efficiency.
- Real-world MPG is typically 10-20% lower than EPA ratings due to driving habits, speed, and environmental conditions.
- 1 US MPG = 0.832674 UK MPG = 0.425144 km/L; use this calculator to convert instantly between all fuel economy units.
- Driving at 55-65 mph instead of 75+ mph can improve fuel economy by 7-14%, saving significant money over time.
- Maintaining correct tire pressure and avoiding excess cargo weight are two of the easiest ways to protect fuel mileage.
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
MPG = Distance (miles) / Fuel (US gallons)
Where:
- \text{MPG}=Miles Per Gallon (US)(mi/gal)
- d_{\text{mi}}=Distance traveled in miles(miles)
- V_{\text{gal}}=Fuel volume in US gallons(US gal)
Worked Examples
American Road Trip - 30 MPG
A sedan travels 300 miles on 10 US gallons of fuel at $3.50/gal.
- 1Convert distance: 300 miles (no conversion needed)
- 2Convert fuel: 10 US gallons (no conversion needed)
- 3US MPG = 300 / 10 = 30.00 MPG
- 4UK MPG = 30 x 0.832674 = 24.98 UK MPG
- 5Distance in km: 300 x 1.60934 = 482.80 km
- 6Fuel in liters: 10 x 3.78541 = 37.85 L
- 7km/L = 482.80 / 37.85 = 12.76 km/L
- 8L/100km = 100 / 12.76 = 7.84 L/100km
- 9Trip cost = 10 gal x $3.50 = $35.00
- 10Cost per mile = $35.00 / 300 = $0.12/mile
European City Car - 12 km/L
A hatchback covers 480 km using 40 liters of petrol.
- 1Distance: 480 km
- 2Fuel: 40 liters
- 3km/L = 480 / 40 = 12.00 km/L
- 4L/100km = 100 / 12 = 8.33 L/100km
- 5Convert to miles: 480 x 0.621371 = 298.26 miles
- 6Convert fuel to US gal: 40 x 0.264172 = 10.567 US gal
- 7US MPG = 298.26 / 10.567 = 28.22 MPG
- 8UK MPG = 28.22 x 0.832674 = 23.50 UK MPG
UK Vehicle - Imperial Gallons
A British car drives 250 miles on 8 imperial gallons of diesel.
- 1Distance: 250 miles
- 2Fuel: 8 UK gallons = 8 x 1.20095 = 9.608 US gallons
- 3US MPG = 250 / 9.608 = 26.02 US MPG
- 4UK MPG = 26.02 x 0.832674 = 21.67 UK MPG
- 5Fuel in liters: 8 x 4.54609 = 36.37 L
- 6Distance in km: 250 x 1.60934 = 402.34 km
- 7km/L = 402.34 / 36.37 = 11.06 km/L
- 8L/100km = 100 / 11.06 = 9.04 L/100km
Introduction
Fuel mileage - also called gas mileage or fuel economy - measures how efficiently a vehicle converts fuel into distance. In the United States, fuel economy is expressed as miles per gallon (MPG); in Europe and most of the world, liters per 100 kilometers (L/100km) or kilometers per liter (km/L) are the standard. This calculator converts seamlessly between all major fuel-efficiency units and optionally estimates your total trip cost.
What Is Fuel Mileage?
Fuel mileage is a measure of how far a vehicle travels on a given amount of fuel. A higher MPG or km/L value means greater efficiency. The U.S. Environmental Protection Agency tests new vehicles and publishes official fuel economy ratings for every model sold in America. Real-world mileage typically differs from EPA ratings by 10-20% depending on driving habits, traffic, and environmental conditions. For a complementary analysis of your fuel costs, try the Fuel Cost Calculator.
How to Calculate Fuel Mileage
To calculate fuel mileage, divide the distance traveled by the amount of fuel consumed: MPG = Distance (miles) / Fuel (US gallons). For metric users: km/L = Distance (km) / Fuel (liters). To convert: 1 US MPG is approximately 0.4251 km/L. The European standard L/100km is the reciprocal: L/100km = 100 / km/L. This means a lower L/100km indicates better efficiency. The MPG Calculator provides a focused view on miles-per-gallon calculations.
Fuel Economy Unit Conversions
Different countries use different fuel economy standards. Key conversions: 1 US MPG = 0.832674 UK MPG (imperial gallon is larger), 1 US MPG = 0.425144 km/L, 1 km/L = 2.35215 US MPG, and 1 L/100km = 235.215 / US MPG. For example, 30 US MPG equals approximately 24.98 UK MPG, 12.76 km/L, or 7.84 L/100km. The Natural Resources Canada Fuel Consumption Guide is an excellent resource for Canadian drivers comparing L/100km ratings.
Factors That Affect Fuel Economy
Many variables influence real-world fuel mileage. Driving speed has the largest impact - fuel economy typically peaks around 50 mph and drops sharply at highway speeds above 70 mph. Tire pressure matters: under-inflated tires increase rolling resistance and can reduce MPG by 0.5% per PSI. Air conditioning reduces fuel economy by up to 25% in hot weather. Cold temperatures reduce engine efficiency. The U.S. Department of Energy publishes detailed tips for improving fuel economy based on decades of real-world data. Use the Fuel Consumption Calculator to track your consumption over time.
Fuel Mileage vs. Fuel Consumption
Fuel mileage (MPG or km/L) and fuel consumption (L/100km or gal/mile) are reciprocals of each other. Mileage tells you how far you go per unit of fuel; consumption tells you how much fuel you use per unit of distance. Improving from 20 to 25 MPG saves more fuel per mile than improving from 40 to 50 MPG - a common misconception called the MPG illusion. European research shows L/100km ratings give consumers a more intuitive sense of real savings. The Fuel Distance Calculator lets you predict range from a full tank. See also U.S. DOE fuel economy research for more context.
Estimating Your Trip Fuel Cost
Trip cost = (Distance / MPG) x Fuel price per gallon. For instance, a 500-mile trip in a 30 MPG vehicle at $3.50/gal costs approximately $58.33. The same trip in a 20 MPG vehicle costs $87.50 - a $29.17 difference. Over 15,000 annual miles, that gap amounts to over $875/year. Our calculator automatically computes total trip cost and cost-per-distance-unit when you enter a fuel price. For full journey planning see the Gas Calculator and the Cost Per Mile Calculator.
Quick Reference Card
Fuel Mileage Quick Reference
Quick reference • Fuel Mileage Calculator
MPG = Distance (mi) / Fuel (US gal) | km/L = Distance (km) / Fuel (L)Valid range: Typical vehicles: 10-60 MPG (4-25 km/L); hybrids: 40-60 MPG; trucks/SUVs: 10-25 MPG
Common Values
⚠ Watch Out
- •EPA ratings are lab results - real-world mileage is typically 10-20% lower.
- •UK gallons (4.546 L) are larger than US gallons (3.785 L) - never mix them up.
- •Short trips under 5 miles significantly reduce average MPG as the engine runs cold.
- •Roof racks and open cargo beds increase drag and can reduce highway MPG by up to 20%.
Pro Tips
- →Fill up at the same station and same pump orientation for consistent readings.
- →Use the brim-to-brim method: fill the tank completely, reset odometer, drive, refill completely, and divide miles by gallons.
- →Log 3-5 fill-ups and average the results for the most reliable real-world MPG figure.
- →Eco-driving techniques (smooth acceleration, anticipatory braking, consistent speed) can improve MPG by 10-30%.
FAQs
What is a good MPG for a car?
A fuel-efficient compact car typically achieves 30-40 MPG in combined city/highway driving. Hybrids can exceed 50 MPG. Most SUVs and trucks range from 15-25 MPG. The EPA considers vehicles achieving above 30 MPG (combined) to be fuel-efficient. In metric terms, 30 MPG is approximately 7.84 L/100km.
How do I reset my car average fuel economy?
Most vehicles with a trip computer have a reset button on the dashboard or steering wheel controls. Resetting it at every fill-up and recording the odometer reading before and after gives you the most accurate real-world MPG. Compare this to the calculation from dividing miles driven by gallons pumped.
Why is my actual MPG lower than the EPA rating?
EPA ratings are measured in controlled laboratory conditions. Real-world driving typically yields 10-20% lower figures due to aggressive acceleration, highway speeds above 65 mph, air conditioning use, cold weather, heavy loads, and traffic congestion. Short trips below 5 miles are especially inefficient because the engine never reaches optimal operating temperature.
What is the difference between US MPG and UK MPG?
The US gallon (3.785 liters) is smaller than the UK imperial gallon (4.546 liters). Because the UK uses a larger gallon, UK MPG values are always higher than US MPG for the same vehicle. To convert: UK MPG = US MPG x 1.20095, or US MPG = UK MPG x 0.832674. A 30 US MPG car achieves about 36 UK MPG.
How does tire pressure affect fuel mileage?
Under-inflated tires create greater rolling resistance, forcing the engine to work harder. The U.S. Department of Energy estimates that every 1 PSI drop in tire pressure reduces fuel economy by approximately 0.5%. Maintaining manufacturer-recommended tire pressure is one of the simplest ways to preserve fuel efficiency.
Can I improve my fuel mileage by driving more slowly?
Yes - aerodynamic drag increases with the square of speed, so fuel consumption rises sharply above 50 mph. The U.S. DOE estimates that every 5 mph over 50 mph is like paying an additional $0.18-$0.28 per gallon. Reducing highway speed from 75 to 65 mph can improve fuel economy by 7-14% depending on the vehicle.