How it works
Pick one period and use the distance and costs from that period throughout. Economic cost measures what the car actually used up: lost value, loan interest and running expenses. Loan principal shows up through the change in value, so full loan payments aren't added in. If the car gained value, depreciation turns negative and brings the total down.
Cash spending is different: it's the gross money that left your account. Include a down payment or cash purchase only if you paid it during this period, along with the full loan payments you made. This basis leaves out depreciation and separate interest so principal and interest aren't counted twice. It also ignores sale proceeds and the equity you keep, so don't call it net ownership cost.
The formula behind the estimate
Every result starts with a defined model and visible assumptions.
Operating cost = period fuel or charging + maintenance + insurance + taxes/registration + other costs Economic cost = operating cost + starting value − ending value + loan interest Gross cash spending = operating cost + acquisition cash paid + full loan payments paid Cost per distance unit = selected period total ÷ recorded distance Monthly average = period total ÷ recorded months
A worked example
Over 12,000 recorded miles, say fuel is $1,400, maintenance $900, insurance $1,500 and taxes $200. Operating costs come to $4,000. If the car's value fell from $20,000 to $18,000 and you paid $600 in interest, economic cost is $6,600, or $0.550 a mile. On a cash basis, with no purchase money paid this period and $3,600 in loan payments, you spent $7,600, or about $0.633 a mile.
Which basis should I use?
Economic cost is better for comparing what a car costs per mile driven. Cash spending explains what left your account in a particular stretch. A paid-off car may have almost no purchase outflow and still lose value. A big down payment can make cash spending look huge in the purchase period even though part of that money stays with you as equity.
Neither number is an official mileage reimbursement rate or a tax deduction. Business-use rules and allowable expenses depend on where you live and your situation.
Why use period totals instead of annual estimates?
A six-month record needs six months of fuel, insurance and interest. Don't pair a full-year insurance premium with half a year of driving unless you want a cash-timing view and label it that way. For economic cost, prepaid expenses may need to be split into a fair share for the period.
A very short period can swing wildly if it includes a major repair or a large purchase payment. A longer record smooths that out. The calculator just divides the totals you give it; it doesn't fill in missing receipts, future maintenance or market values.
Questions worth asking
How do I calculate a car's cost per mile?
Add up the costs for one period on a single consistent basis, then divide by the distance you drove in that period. This calculator does that for both an economic and a cash basis.
Should I include the full loan payment?
Only on the cash-spending basis. The economic basis uses the change in value plus interest, so counting principal repayments as well would count the car's price twice.
Can the economic cost come out negative?
Yes, if the value gain you entered is bigger than the other costs. Check that your starting and ending values cover the same period.
Is this a tax mileage rate?
No. It's your own cost calculation and doesn't set an allowable deduction or reimbursement.
Can I calculate cost per kilometer?
Yes. Switch units and the tool converts the recorded distance and shows cost per kilometer, with the same total period cost.
This is general information, not personalized financial advice. Read the limitations.
