Distance, mpg and price — that is the whole sum
Distance divided by miles per gallon gives the gallons you will use; multiply that by the pump price for the trip cost. A 300-mile drive at 25 mpg needs 12 gallons, so at $3.80 it costs $45.60. In metric it is the same idea: (km ÷ 100) × L/100 km × price per litre.
A 500-mile trip by vehicle type
| Vehicle | mpg | Gallons | Cost at $3.80 |
|---|---|---|---|
| Pickup truck | 18 | 27.8 | $105.60 |
| SUV | 22 | 22.7 | $86.30 |
| Sedan | 28 | 17.9 | $67.90 |
| Hybrid sedan | 40 | 12.5 | $47.50 |
Same road, same fuel price — the truck costs more than double the hybrid. Over a year of driving that gap is where fuel savings actually come from.
What throws the estimate off
- Real-world mpg is lower. Shave 15–25% off the sticker figure for honest numbers. Cold starts, city stop-go and a loaded roof rack all cost fuel.
- Speed matters. Above about 55 mph, every extra 5 mph knocks off roughly 5% of your mpg. Driving 70 instead of 55 can use about 20% more fuel.
- Price is the volatile part. Pump prices move week to week and by region. Use today's local price, not last month's, for a trip you are planning now.
Common questions
How do I work out the fuel cost of a trip?
Divide the distance by your miles per gallon to get the gallons you will burn, then multiply by the price per gallon. For 300 miles at 25 mpg and $3.80 a gallon: 300 / 25 = 12 gallons, times 3.80 is $45.60.
What is a quick way to estimate it in my head?
For a typical 25 mpg car, roughly divide the miles by 20 and multiply by the fuel price. 500 miles at $4 a gallon is about 500 / 20 x 4 = $100. It is a rough figure but close.
Why is my real cost higher than the estimate?
The window-sticker (EPA) mpg is measured under ideal conditions. Real driving with cold weather, air conditioning, hills or highway speeds above 60 mph can cut your mpg by 15 to 25%, which raises the cost by the same amount.
