How to calculate the full cost of a UK commute

Fuel is only one part of a commute’s cost. To estimate what driving costs you each week, use your own mileage, your vehicle’s real-world fuel economy and a current local pump price, then add parking, tolls and other journey expenses. Compare that total with public transport on the same days and routes.

Calculate weekly fuel use from your own mileage

Start with the miles you actually drive for commuting in a typical week, including the return journey. If you make extra trips for work, include those too. Your car’s miles per gallon (mpg) tells you how many miles it travels on a gallon of fuel.

For UK fuel prices quoted per litre, convert gallons to litres. One imperial gallon—the unit normally used for UK mpg—is approximately 4.546 litres. The calculation is:

Weekly commute miles ÷ miles per gallon × 4.546 × price per litre = estimated weekly fuel cost

Use imperial mpg, as shown by most UK car displays and specifications. Do not use US mpg with this conversion. If you track fuel purchases, your actual consumption over several weeks can give a better estimate than a dashboard figure or published test result.

Worked example with clearly labelled assumptions

Assumptions: A 40-mile daily round trip, five commuting days a week, a car averaging 40 imperial mpg, and fuel priced at £1.50 per litre. These are example figures only, not current UK prices.

• Weekly distance: 40 × 5 = 200 miles
• Fuel used: 200 ÷ 40 = 5 imperial gallons
• Fuel in litres: 5 × 4.546 = about 22.7 litres
• Estimated fuel cost: 22.7 × £1.50 = about £34.05 a week

At the same mileage and assumed price, a car averaging 50 mpg would use about 18.2 litres, costing roughly £27.30. The difference is an estimate: traffic, weather, driving style, vehicle load and maintenance can all change real-world consumption.

Add the costs beyond the pump

A cheaper filling station does not automatically make a commute cheaper. A detour to reach a lower price can add miles, time and fuel, while a route with expensive parking or tolls can outweigh a saving at the pump.

Build a weekly comparison that includes the costs that apply to your journey:

• Parking: Include daily charges, workplace permits or a regular monthly fee divided across the weeks you use it.
• Tolls and road charges: Count charges on the route and any fees that apply to the vehicle or travel area.
• Extra distance: Add fuel for a detour to a cheaper station or a longer route around congestion.
• Vehicle costs: If you want a broader ownership comparison, account separately for maintenance, tyres, insurance, tax and depreciation. These are not all directly changed by one commute, so state how you allocate them.
• Public transport: Compare fares for the same number of journeys and days. Check whether a season ticket, carnet or off-peak fare applies, and include any connecting bus, train or parking cost.

For a fair comparison, use the same week and journey pattern for each option. A single-occupant car may cost more per person than a bus or train; if several people share the trip, divide only the costs they genuinely share. Also consider the time and reliability of each route, even if you keep those outside the cash total.

Compare local prices using dated information

Local prices can vary by station and change over time. Check a live or recently updated local price listing before filling up, and note the date and time shown. Confirm the price at the pump when you arrive; a listing may be delayed or a particular fuel grade may differ.

For a national benchmark, the Department for Energy Security and Net Zero publishes monthly UK road fuel price statistics. Monthly figures provide context for price trends, but they are not a live quote for a specific station. Check the publication month before using a figure and do not treat an undated average as today’s price.

Make the comparison useful for your next journey

Use a recent week of commuting rather than your best-case journey. Record the round-trip miles, days travelled, fuel economy, dated local price and any parking or toll charges. Recalculate when your route, schedule or vehicle changes, or when you check a new pump price.

A lower per-litre price matters most when the station is convenient and the amount saved exceeds any added journey cost. Comparing the complete weekly total gives you a more useful budget than looking at the pump price alone.

Source: UK Department for Energy Security and Net Zero