Automotive
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Fuel Economy Calculator.
Calculate MPG and fuel costs for trips
Set your values
Results update as you type.
How to Use
Calculate your vehicle's fuel economy and costs:
- Miles per gallon (MPG) or kilometers per liter
- Fuel costs per mile/kilometer
- Daily, weekly, monthly, and yearly fuel costs
- Driving range with full tank
How to Use the Fuel Economy Calculator
The Fuel Economy Calculator helps you calculate your vehicle's fuel efficiency (MPG or L/100km) and estimate fuel costs for trips. Track your vehicle's performance and make informed decisions about fuel efficiency.
- Calculate miles per gallon (MPG) or liters per 100km (L/100km).
- Estimate fuel costs for planned trips.
- Compare fuel efficiency between different vehicles.
- Track fuel economy over time to identify efficiency changes.
- Calculate total trip costs including fuel.
Fuel Economy Formulas
Understanding fuel efficiency calculations helps you budget for trips and identify potential vehicle maintenance issues.
Miles Per Gallon (MPG)
MPG measures how many miles your vehicle travels per gallon of fuel.
Example:
Input: Miles driven: 300 miles, Fuel used: 12 gallons
Calculation: 300 ÷ 12
Result: 25 MPG
Liters Per 100km (L/100km)
European standard for fuel efficiency; lower numbers indicate better efficiency.
Example:
Input: Fuel: 8 liters, Distance: 100 km
Calculation: (8 ÷ 100) × 100
Result: 8 L/100km
Fuel Cost for Trip
Calculates the fuel cost for a planned journey.
Example:
Input: Distance: 300 miles, MPG: 25, Fuel price: $3.50/gallon
Calculation: (300 ÷ 25) × $3.50
Result: $42
MPG to L/100km Conversion
Converts between imperial and metric fuel efficiency measurements.
Example:
Input: MPG: 25
Calculation: 235.2 ÷ 25
Result: 9.4 L/100km
Real-World Use Cases
Fuel economy calculations help with trip planning, vehicle purchasing decisions, and identifying maintenance issues.
Trip Budgeting
Estimate fuel costs before long road trips to plan your budget and identify the most economical routes.
Vehicle Comparison
Compare fuel efficiency between vehicles to make informed purchasing decisions and calculate long-term ownership costs.
Maintenance Monitoring
Track fuel economy over time to identify sudden efficiency drops that may indicate mechanical problems.
Eco-Friendly Driving
Monitor and improve your fuel economy to reduce emissions and environmental impact of your driving.
Business Expense Tracking
Calculate fuel expenses for business vehicle deductions and reimbursement claims.
Tips & Best Practices
Tips
- Check tire pressure regularly; underinflated tires reduce fuel economy by up to 3%.
- Combine trips to reduce total distance driven and fuel consumption.
- Accelerate smoothly and avoid excessive idling to improve fuel efficiency.
- Remove excess weight from your vehicle; every 100 lbs reduces MPG by about 1%.
- Highway driving is typically more efficient than city driving for most vehicles.
Common Mistakes to Avoid
- Not resetting trip odometer when filling up, leading to inaccurate calculations.
- Comparing city and highway fuel economy without considering driving conditions.
- Ignoring tire pressure and maintenance factors that significantly affect fuel economy.
- Using instantaneous fuel economy displays instead of calculating over full tanks.
Related Calculators
Cite this calculator
Canonical URL: https://mathify.one/en/automotive/fuel-economy
Cite as: Mathify. (2026). Fuel Economy Calculator. https://mathify.one/en/automotive/fuel-economy
Use Cases
Plan a road trip budget
Estimate the fuel cost for a planned trip by entering the total distance, expected fuel consumption, and current fuel price.
Example: Enter distance 500 miles, fuel used 20 gallons, fuel price $3.50/gal to get a cost of $70.
Monitor your vehicle's fuel efficiency
Track your car's MPG over time by entering distance and fuel used after each fill-up to see if your vehicle is performing well.
Example: After driving 300 miles and using 10 gallons, your MPG is 30.
Frequently Asked Questions
- How do I calculate MPG with this calculator?
- Enter the distance traveled and the fuel used (in gallons or liters) in the corresponding fields. The calculator will divide distance by fuel used to give you your miles per gallon (MPG).
- What is the fuel cost for a trip?
- Input the distance of your trip, the fuel used, and the fuel price per unit. The calculator multiplies fuel used by fuel price to estimate the total fuel cost for that trip.
- Can I estimate my driving range on a full tank?
- Yes, if you provide your tank size and daily miles, the calculator can estimate how many miles you can drive on a full tank and how many days that might last based on your average daily driving.
Tips & Common Mistakes
Tips
- For accurate MPG, fill your tank completely, reset your trip odometer, and drive until the next fill-up. Then enter the exact distance and fuel used.
- Use the same units (miles/gallons or kilometers/liters) for distance and fuel to get consistent results.
- Check your fuel price at the pump or use a local average for more precise cost estimates.
- If you know your tank size and daily miles, you can estimate how often you'll need to refuel.
Common Mistakes to Avoid
- Mixing units: entering distance in miles but fuel in liters will give incorrect MPG. Stick to one unit system.
- Not resetting the trip odometer before measuring, leading to inaccurate distance input.
- Forgetting to include the fuel price per unit, which results in missing the cost calculation.
Last updated: August 13, 2026