Automotive
Trip fuel and charging costs, real consumption and child car seat rules.
- Car seat law UK checkerEnter a child's age, height and weight, the seat and the situation, and the checker applies the child car seat rules of Great Britain to that journey. It shows whether a child seat is needed, whether the front seat is allowed, and what a breach costs. Rules checked on 28 September 2026.
- Fuel cost calculatorEnter the distance in miles, your car's miles per gallon and the pump price, and the page works out the fuel a journey burns and what it costs, one way or there and back, and per passenger if you share. For an electric car, enter miles per kWh and your electricity price instead. Switch to the fill-up mode to measure the economy your car really achieves. The starting prices are the UK averages for the week of 21 September 2026.
What the motoring tools here work out
The Automotive tools start from the question most drivers actually ask: what will this journey cost? The fuel cost calculator takes the distance in miles, your car's miles per gallon and the pump price per litre, then gives the fuel burned and the cost, one way or there and back. Add the number of people in the car and it splits the bill evenly, which is the usual way to share a lift when nobody is making money from it.
- Petrol or diesel: miles per imperial gallon, converted to litres because forecourts price by the litre.
- Electric: miles per kWh and a tariff in pence per kWh, for charging at home or anywhere else you know the rate.
- Fill-up mode: brim the tank, note the miles, refill, and it measures the economy your car really achieves rather than the brochure figure.
The result also shows litres per 100 km alongside mpg, handy when comparing with a continental review or a hire car's dashboard.
Child car seats: the rules for each journey
The child car seat checker answers a question about the passengers rather than the fuel: does this child still need a car seat? In Great Britain a child uses one until reaching 12 years or 135 cm, whichever comes first. The checker also covers taxis, unexpected journeys and a third child with no room for another seat.
Enter the age, height, weight, seat and situation. The result says whether a child seat is required, whether the front seat is allowed with that seat and airbag setting, and what a breach costs: a £100 fixed penalty, or up to £500 in court.
Where the starting prices and taxes come from
The petrol and diesel prices filled in for you are UK averages from the government's weekly road fuel price statistics (DESNZ), for the week of 21 September 2026. The electricity rate is the Ofgem price cap unit rate for 1 October 2026 to 31 December 2026. Fuel duty is a fixed amount per litre (HMRC), and VAT is charged on top of the price including duty, so at the average unleaded price about 47% of what you pay is tax.
Averages go out of date as prices move from week to week, and the price at your local forecourt can sit well above or below them. Every figure is only a starting value: type over it with the price on the pump or your own tariff. How the averages are chosen and checked is set out in the methodology, and the tool page lists each source with the date it was verified.
Reading the result
Any fuel cost here is an estimate. Real consumption shifts with speed, traffic, cold starts, load, tyre pressure and the weather, and a motorway run and a school run in the same car can differ widely. A measured figure from the fill-up mode is usually closer to your own driving than the manufacturer's official number.
The cost per mile covers fuel or electricity only. It leaves out insurance, servicing, tyres, depreciation and parking. That is why HMRC's Approved Mileage Allowance Payments, described on the tool page, sit above the fuel cost: they are meant to cover running a car as a whole. The page explains these rates; it does not say what anyone should claim or charge.