Fuel Cost Calculator
Planning a road trip or comparing two cars? Enter your distance, your car’s MPG and the gas price to see your total fuel cost, how many gallons you’ll use, and what each mile costs you.
Estimated Total Trip Cost
How It Works
The maths is simple division and multiplication. First the calculator works out how many gallons your trip needs: distance divided by your car’s miles per gallon (MPG). Then it multiplies those gallons by the price per gallon to get the total trip cost. Cost per mile is the price per gallon divided by MPG — a handy number for comparing cars or deciding whether driving beats flying.
MPG is the number that matters most: a car rated at 40 MPG uses half the fuel of one rated at 20 MPG over the same distance. Real-world MPG is usually a little lower than the official figure, especially in stop-and-go traffic or with a loaded car — if you know your true MPG from past fill-ups, use that instead.
Worked Example
A 300-mile trip at 30 MPG needs 300 ÷ 30 = 10 gallons. At $3.50 a gallon, the trip costs 10 × $3.50 = $35.00, and cost per mile is $3.50 ÷ 30 = $0.1167, about 12 cents a mile. The same trip in a 20 MPG SUV costs $52.50 — an extra $17.50.
Assumptions
- MPG stays constant for the whole trip; in reality it varies with speed, hills and traffic.
- The gas price you enter applies to the whole trip.
- No tolls, parking or wear-and-tear costs are included — this is fuel only.
- Distance is in miles and fuel in US gallons.
The same 300-mile trip at $3.50 a gallon, by car:
| Car MPG | Gallons used | Trip cost | Cost per mile |
|---|---|---|---|
| 20 MPG | 15.0 gal | $52.50 | $0.175 |
| 25 MPG | 12.0 gal | $42.00 | $0.140 |
| 30 MPG | 10.0 gal | $35.00 | $0.117 |
| 35 MPG | 8.6 gal | $30.00 | $0.100 |
| 40 MPG | 7.5 gal | $26.25 | $0.088 |
How to Use This Calculator
Enter the one-way distance, your MPG and the price per gallon. The result updates live, with a breakdown of gallons used and cost per mile, and you can print it as a PDF for your trip budget.
Tips and Practical Advice
Compare cars by cost per mile, not just MPG: the gap between 20 and 30 MPG is worth about 6 cents a mile at $3.50 a gallon — about $580 over 10,000 miles. Keep your tyres inflated and your speed steady on the highway, and check gas prices along the route: a 30-cent difference per gallon saves $3.00 on every 10 gallons.
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