Fuel: price per gallon ÷ miles per gallon (US), or litres per 100 km × price per litre (metric). Idling, APU fuel, reefer fuel and fuel burned in traffic all show up as a worse real-world mpg — so use the number off your fuel receipts, not the sticker.
Fixed costs are the ones that punish you for sitting still. They are divided by the miles you actually run, which is why a truck doing 2,500 miles a week can be beaten by one doing 3,000 at the same rates, and why a cheap load that keeps you rolling is often not as cheap as it looks — the sensitivity table below shows exactly what the extra miles do.
What is not here: tax. IFTA, income tax, the cost of money, driver benefits, permits for oversize loads and the price of a breakdown at the wrong moment. This is an operating-cost model, not an accountant's P&L. Depreciation is whatever your payment or your own figure says it is.
Information, not financial advice. Your tax position and your risk belong to a professional, and the numbers belong in a spreadsheet once a month whether you like spreadsheets or not.