Mileage Calculator
Calculate your trip fuel cost or measure your vehicle's fuel efficiency. Switch between Trip Cost and Fuel Efficiency modes, toggle Imperial or Metric units, and get instant results including fuel needed, total cost, and cost per mile or kilometer.
How the Mileage Calculator Works
This mileage calculator operates in two modes to cover every fuel-related question. In Trip Cost mode, you enter your planned distance, your vehicle's fuel efficiency, and the current fuel price. The calculator determines exactly how much fuel you need and what it will cost, including a per-mile or per-kilometer breakdown. In Fuel Efficiency mode, enter the distance you traveled and the amount of fuel you used, and the calculator computes your actual MPG, km/L, and L/100km so you can compare against manufacturer ratings.
Mileage Calculator Formulas
Fuel Needed = Distance ÷ Fuel Efficiency (MPG or km/L)
Total Cost = Fuel Needed × Fuel Price
Cost Per Mile = Total Cost ÷ Distance
MPG = Distance (miles) ÷ Fuel Used (gallons)
L/100km = (Fuel Used in L ÷ Distance in km) × 100
Tips to Improve Fuel Efficiency
Small changes in driving habits can meaningfully reduce fuel costs over time. Maintain steady speeds on the highway and use cruise control when possible — speed fluctuations waste fuel. Keep tires inflated to the recommended pressure, since underinflated tires increase rolling resistance by up to 3 percent. Remove roof racks and heavy cargo when not in use, as extra weight and aerodynamic drag force the engine to work harder. Avoid idling for more than 30 seconds; modern engines use less fuel restarting than idling. Regular oil changes with the manufacturer-recommended grade keep the engine running efficiently, and a clean air filter improves combustion and reduces consumption.
MPG vs L/100km — Understanding Fuel Economy
The United States measures fuel economy in miles per gallon (MPG), where a higher number is better. Most of Europe, Australia, and Asia use liters per 100 kilometers (L/100km), where a lower number is better. This inverse relationship can cause confusion when comparing vehicles across systems. For example, a car rated at 30 MPG consumes about 7.8 L/100km, while 40 MPG equals roughly 5.9 L/100km. Japan and parts of South America use km/L, which behaves like MPG — higher is more efficient. This calculator converts between all three systems automatically, so you always see your results in the format you prefer.
Mileage Calculator for Road Trips
Planning a road trip budget starts with accurate fuel cost estimation. Enter your total trip distance, your vehicle's real-world fuel efficiency (not the manufacturer sticker — check your trip computer), and the average fuel price along your route. The calculator returns total fuel needed, total cost, and cost per mile or kilometer. For multi-day trips, remember that highway driving is typically 10 to 15 percent more efficient than city driving, and fuel prices can vary significantly by region. Filling up before crossing into states or countries with higher fuel taxes can save meaningful amounts on longer journeys.
Frequently Asked Questions
How do I calculate mileage for a road trip?
To calculate mileage cost for a road trip, divide your total distance by your vehicle's fuel efficiency (MPG or km/L) to find fuel needed, then multiply by the current fuel price. For example, a 300-mile trip at 30 MPG with gas at $3.50 per gallon needs 10 gallons, costing $35. This mileage calculator handles both Imperial and Metric units automatically.
What is a good MPG rating for a car?
A good MPG depends on vehicle type. Compact cars typically achieve 30-40 MPG, midsize sedans 25-35 MPG, SUVs 20-28 MPG, and trucks 15-22 MPG. Hybrid vehicles often reach 45-60 MPG. For reference, the EPA considers anything above 30 MPG combined to be fuel-efficient for a non-hybrid passenger car.
How do I convert MPG to L/100km?
To convert MPG (US) to L/100km, divide 235.215 by the MPG value. For example, 30 MPG equals 235.215 / 30 = 7.84 L/100km. Note that MPG uses an inverse scale (higher is better) while L/100km uses a direct scale (lower is better). This calculator displays both units automatically so you never need to convert manually.
How do I calculate my car's actual fuel efficiency?
Fill your tank completely, reset your trip odometer, drive normally until you need to refuel, then fill up again and note the gallons or liters added. Divide the miles or kilometers driven by the fuel added. For example, 350 miles on 12 gallons equals 29.2 MPG. Repeat over several fill-ups for a more accurate average. Use the Fuel Efficiency mode of this calculator to do the math instantly.
Does driving speed affect fuel efficiency?
Yes, significantly. Most vehicles reach peak fuel efficiency between 45-65 mph (72-105 km/h). Above 65 mph, aerodynamic drag increases exponentially — every 5 mph over 50 mph is roughly equivalent to paying an extra $0.20 per gallon. Driving at 80 mph can reduce fuel economy by 15-30% compared to 60 mph. Maintaining a steady speed with cruise control on highways is one of the most effective ways to maximize mileage.
What is the difference between city and highway MPG?
City MPG measures fuel efficiency during stop-and-go urban driving with frequent braking and acceleration, which consumes more fuel. Highway MPG measures efficiency at steady cruising speeds, which is typically 20-30% better than city MPG. The EPA combined rating uses a weighted average of 55% city and 45% highway driving. Your actual mileage depends on your personal mix of city and highway driving.
How much does tire pressure affect gas mileage?
Underinflated tires can reduce gas mileage by about 0.2% for every 1 PSI drop in pressure across all tires. If your tires are 10 PSI below recommended, you could be losing 2% or more in fuel economy, which adds up to an extra gallon of gas every few fill-ups. Check tire pressure monthly when tires are cold and inflate to the specification on the driver-side door sticker, not the number on the tire sidewall.