How trip fuel cost is calculated
Fuel needed = distance ÷ MPG (or distance × L/100 km ÷ 100) · Cost = fuel needed × price
Worked examples
- US: 250 miles at 28 MPG = 8.93 gallons × $3.40 = $30.36.
- UK: 200 miles at 45 MPG = 4.44 imperial gallons = 20.2 litres × £1.45 = £29.30. Return trip shared by 3: £19.53 each.
- Metric: 500 km at 6.5 L/100 km = 32.5 litres × €1.80 = €58.50.
Gas cost by distance and MPG (at $3.40 per gallon)
| Distance | 20 MPG | 25 MPG | 30 MPG | 40 MPG |
|---|---|---|---|---|
| 100 miles | $17 | $14 | $11 | $9 |
| 250 miles | $43 | $34 | $28 | $21 |
| 500 miles | $85 | $68 | $57 | $43 |
| 1000 miles | $170 | $136 | $113 | $85 |
Tips for a cheaper trip
- Speed matters most: above about 50–60 mph, consumption rises quickly with aerodynamic drag.
- Check tire pressures before setting off — under-inflated tires waste fuel.
- Roof boxes and bike racks can add 10–25 % at motorway speeds; remove them when not in use.
Frequently asked questions
How do I calculate the gas cost of a trip?
Divide the distance by your fuel economy to get the gallons (or litres) needed, then multiply by the price per gallon (or litre). For 300 miles at 25 MPG and $3.50 per gallon: 300 ÷ 25 = 12 gallons × $3.50 = $42.
Which MPG figure should I use?
Your own measured MPG is best (use the MPG calculator after a fill-up). Otherwise use the official highway figure for mostly motorway trips and the combined figure for mixed driving, then add a margin for luggage, roof boxes, air-con and speed.
Why does the UK option use price per litre?
UK fuel is sold by the litre but car economy is quoted in imperial MPG. The calculator converts between imperial gallons (4.546 L) and litres for you.
Does the calculator include tolls or wear?
No — it is fuel only. For a full running cost add tolls, parking and roughly 10 to 20 cents per mile for tires, maintenance and depreciation.