Fuel budgeting
How to calculate fuel cost
A useful fuel budget needs three consistent inputs: distance, fuel use and the price per unit of fuel.
Start with a matching set of units
For km/L, divide kilometres by economy to find litres. For L/100km, multiply kilometres by the consumption figure and divide by 100. Multiply litres by the price per litre. With MPG, use the matching US or UK gallon throughout, or convert first.
Build a realistic annual distance
A commute of 40 km on five days a week is 200 km/week before other driving. If you drive it for 46 weeks, that is 9,200 km. Add leisure and other travel separately. Entering 40 km/day into a 365-day calculator would instead assume 14,600 km/year.
Check the worked budget
At 1,000 km/month, 12 km/L and 1.50 per litre, you use 83.33 litres and spend 125 per month. Twelve months cost 1,500. This excludes servicing, insurance, depreciation and parking, so it is a fuel budget rather than total ownership cost.
Method and references
Examples use nominal geometry and fixed-price scenarios, with no vehicle-specific specifications implied. See our calculation methodology and editorial policy.
Unit reference: NIST Guide to the SI: conversion factors. Financial examples are arithmetic illustrations, not market-price forecasts.