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Gas Mileage Calculator

Calculate your fuel economy in MPG or L/100km.

Last updated: June 13, 2026

Calculator

Distance Traveled

miles

Fuel Used

gallons

Fuel Price (optional)

$/gal

Results

Fuel Economy25.0 MPG

Metric9.4 L/100km

Cost per Mile$0.14

Total Fuel Cost$42.00

How to Use This Calculator

1Enter the total distance traveled in miles.
2Enter the total fuel used in gallons.
3Optionally enter fuel price per gallon to see cost analysis.

Formula Explanation

Gas mileage (MPG) is calculated by dividing total distance by total fuel consumed. The metric equivalent (L/100km) uses a conversion factor.

MPG = Distance (miles) ÷ Fuel Used (gallons) L/100km = 235.215 ÷ MPG Cost per Mile = (Fuel Used × Price per Gallon) ÷ Distance

Variables:

MPGMiles Per Gallon — higher is better

L/100kmLiters per 100 kilometers — lower is better

Worked Examples

300 miles on 12 gallons at $3.50/gal

1. MPG = 300 ÷ 12 = 25 MPG
2. L/100km = 235.215 ÷ 25 = 9.4
3. Cost per mile = (12 × $3.50) ÷ 300 = $0.14

Result: 25 MPG | $0.14 per mile | $42.00 total fuel cost

450 miles on 15 gallons

1. MPG = 450 ÷ 15 = 30 MPG
2. L/100km = 235.215 ÷ 30 = 7.8

Result: 30 MPG (7.8 L/100km)

Why Use This Calculator

Track fuel efficiency over time to catch declining engine performance.
Compare actual MPG to EPA estimates for your vehicle.
Calculate the real cost of your commute or road trip.
Make informed decisions about vehicle purchases based on fuel costs.

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Tips & Best Practices

Fill up completely and reset your trip odometer for the most accurate reading.
Track MPG over several tanks for a reliable average — one tank can vary significantly.
Highway MPG is typically 15–30% better than city MPG.
Low tire pressure, dirty air filters, and aggressive driving all reduce fuel economy.

Common Mistakes to Avoid

❌ Calculating MPG from a partial fill-up.

✅ Always fill the tank completely for start and end measurements.

❌ Using the trip odometer instead of actual miles driven.

✅ Both work, but ensure you reset the odometer at the same time you fill up.

❌ Not accounting for different driving conditions when comparing.

✅ Compare city-to-city and highway-to-highway separately for meaningful analysis.

Frequently Asked Questions

What is good gas mileage?

A combined MPG of 25–30 is average for modern sedans. Hybrid vehicles achieve 40–60 MPG. Trucks and SUVs typically get 18–25 MPG. Your driving conditions heavily influence actual results.

Why is my actual MPG lower than the EPA rating?

EPA tests are conducted under controlled conditions. Real-world factors like aggressive driving, cold weather, city traffic, roof racks, and heavy cargo all reduce MPG below EPA estimates.

How can I improve my gas mileage?

Maintain proper tire pressure, drive at moderate speeds, avoid rapid acceleration, reduce idling, keep up with maintenance (air filter, spark plugs), and remove unnecessary weight from your vehicle.

Does cruise control save gas?

Yes, on highways. Cruise control maintains a constant speed which is more fuel-efficient than human throttle variations. However, turn it off on hilly terrain where it may over-accelerate.

Is premium gas worth the extra cost?

Only if your vehicle requires it. Most cars run perfectly on regular (87 octane). Using premium when not required provides no MPG or performance benefit.

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Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.

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