How to calculate gas cost for a trip
- Total miles ÷ MPG = gallons needed.
- Gallons × price per gallon = fuel cost.
Example: a 250-mile drive each way is 500 miles round trip. At 28 MPG that is about 17.9 gallons; at $3.20 a gallon the fuel costs about $57. Split between two people, $28.57 each.
Fuel cost for 100 miles
| MPG | $3.00/gal | $3.50/gal | $4.00/gal | $4.50/gal |
|---|---|---|---|---|
| 15 | $20.00 | $23.33 | $26.67 | $30.00 |
| 20 | $15.00 | $17.50 | $20.00 | $22.50 |
| 25 | $12.00 | $14.00 | $16.00 | $18.00 |
| 30 | $10.00 | $11.67 | $13.33 | $15.00 |
| 35 | $8.57 | $10.00 | $11.43 | $12.86 |
| 40 | $7.50 | $8.75 | $10.00 | $11.25 |
| 50 | $6.00 | $7.00 | $8.00 | $9.00 |
Tips to spend less on gas
- Keep tires properly inflated and remove unused roof racks.
- Drive at steady speeds; aggressive acceleration and very high speeds lower MPG.
- Compare gas prices along your route — prices can vary a lot between nearby stations.
- Carpool and split costs for holiday travel.
UK and metric versions of the formula
- UK (miles per gallon, price per litre): litres = miles ÷ MPG × 4.546, because a UK (imperial) gallon is 4.546 litres. A US gallon is smaller, 3.785 litres, so UK MPG figures look higher for the same car.
- Kilometres and L/100 km (Canada, Australia, New Zealand, Europe): litres = km × L/100 km ÷ 100. A 400 km trip at 7 L/100 km uses 28 litres; at 1.80 a litre that is 50.40.
Fuel cost for 100 km
| L/100 km | 1.50 / L | 1.75 / L | 2.00 / L | 2.25 / L |
|---|---|---|---|---|
| 4 | 6.00 | 7.00 | 8.00 | 9.00 |
| 5 | 7.50 | 8.75 | 10.00 | 11.25 |
| 6 | 9.00 | 10.50 | 12.00 | 13.50 |
| 7 | 10.50 | 12.25 | 14.00 | 15.75 |
| 8 | 12.00 | 14.00 | 16.00 | 18.00 |
| 10 | 15.00 | 17.50 | 20.00 | 22.50 |
| 12 | 18.00 | 21.00 | 24.00 | 27.00 |
Thanksgiving travel tip: the Wednesday before Thanksgiving (November 25, 2026) and the Sunday after (November 29) are traditionally among the busiest travel days. Leaving earlier in the day can save time and fuel spent in traffic.
Gas Cost Calculator FAQs
How do I calculate gas cost for a road trip?
Divide the total miles by your car's MPG to get gallons, then multiply by the price per gallon.
How much gas does it take to drive 100 miles?
Divide 100 by your MPG. A 25-MPG car uses 4 gallons per 100 miles.
How do I find my car's MPG?
Check the window sticker or the EPA fuel-economy listing for your model, or fill the tank, reset the trip meter, and divide miles driven by gallons used at the next fill-up.
How should passengers split gas money?
A common approach is to divide the fuel cost evenly. Some groups also add parking and tolls.