Travel Cost Calculator
Estimate what a journey actually costs in fuel and time, and compare driving against the alternatives on a fair basis.
Formula
Fuel cost = distance ÷ miles per gallon × price per gallon
- In metric: litres = distance (km) × L/100km ÷ 100
- A UK gallon is 4.546 litres, so price per gallon = price per litre × 4.546
300 miles at 45 mpg with fuel at £1.45 a litre: 30.3 litres, £43.94
Fuel Cost
Fuel cost = (Distance ÷ Fuel economy) × Price per unit
In UK terms, with economy in miles per gallon and fuel priced per litre, convert first: one imperial gallon is 4.546 litres.
A 300-mile trip at 45 mpg uses 6.67 gallons, or 30.3 litres. At £1.45 a litre that is about £44.
Fuel Is Not the Whole Cost
Fuel is the visible expense and rarely the largest. HMRC's approved mileage rate of 45p per mile for the first 10,000 business miles exists precisely because it covers the full running cost: depreciation, tyres, servicing, insurance and tax.
By that measure the same 300-mile trip costs about £135, roughly three times the fuel alone.
Add parking, tolls and the Dartford Crossing or congestion charges where relevant.
Comparing Fairly
Driving costs are usually per vehicle, while train fares are per person. A four-person journey shifts the comparison substantially, and a solo one shifts it back.
Time deserves counting too: mapping apps quote optimistic durations that assume no traffic and no stops. Add roughly 15 minutes per two hours for breaks, and remember that a train journey lets you work while a drive does not.
Quick Reference
| Round trip | At 35 mpg | At 45 mpg | At 55 mpg |
|---|---|---|---|
| 100 miles | £18.83 | £14.65 | £11.98 |
| 300 miles | £56.50 | £43.94 | £35.95 |
| 500 miles | £94.17 | £73.24 | £59.92 |
| 1,000 miles | £188.33 | £146.48 | £119.85 |
Frequently Asked Questions
- How do I calculate fuel cost for a trip?
- Divide distance by miles per gallon, convert gallons to litres by multiplying by 4.546, then multiply by the price per litre.
- What does driving actually cost per mile?
- HMRC's 45p per mile rate reflects total running costs including depreciation, servicing and insurance. Fuel alone is typically around a third of that.
- Is driving cheaper than the train?
- It depends on occupancy. Car costs are per vehicle and rail fares per person, so a full car usually wins and a solo driver often does not.
- How accurate are estimated journey times?
- Mapping apps assume clear traffic and no stops. Add roughly 15 minutes of break per two hours of driving for a realistic figure.