TaxBuddieSign inCreate AccountHow the fuel cost is calculated
The calculator divides miles by imperial MPG to estimate gallons, converts gallons to litres, then multiplies by the entered price per litre. The cost-per-mile result is the estimated fuel cost divided by journey miles.
Use actual fill-ups for business records
This estimate is helpful for planning, but actual receipts and mileage give stronger evidence. A tank can cover several business and private journeys, and displayed MPG can differ from actual consumption.
Fuel cost and tax deductions are different
If an eligible self-employed driver uses simplified mileage, fuel is already represented by the flat rate. If using actual vehicle costs, only the business proportion of fuel and other running costs is considered. The choice has wider rules than this journey estimate.
Fuel calculator FAQs
Does it use US or UK gallons?
UK imperial gallons. One imperial gallon is 4.54609 litres.
Can I use dashboard MPG?
Yes for an estimate, but measured fill-to-fill consumption can be more representative.
Is the result an allowable expense?
Not by itself. Your tax method, business-use share, evidence and journey purpose determine the allowable amount.
Official guidance
Important: Planning estimate only. Consumption and prices vary. TaxBuddie provides record keeping and exports; it does not submit tax returns or MTD updates.