UK units
Fuel tools are adapted to miles, imperial MPG and pence per litre. HMRC guidance itself uses miles, MPG and pence-per-mile fuel rates, while the Vehicle Certification Agency discusses fuel cost over 10,000 miles.
Changing prices
AutoCifra does not claim that one hard-coded petrol, diesel or electricity price is permanently “current”. You enter the price relevant to the scenario you want to calculate.
Useful official UK sources
GOV.UK — Advisory fuel ratesOpen GOV.UK
GOV.UK — Mileage and fuel allowancesOpen GOV.UK
Vehicle Certification Agency — Fuel consumption and costOpen VCA
Limitations
The calculators are estimates. They do not know the condition of your vehicle, future prices, your tax position, traffic or individual insurance terms.
Privacy of calculations
The arithmetic runs in your browser and does not require AutoCifra to store the numbers you enter in a database.