This calculator works out what it really costs you to drive one kilometre in New Zealand, from the fuel in the tank to the costs that quietly add up in the background. Most people think of driving cost as the price of petrol, but the full picture is wider. There is the fuel itself, which depends on your car's economy and the pump price; there are road user charges, which diesel and electric light vehicles pay instead of fuel excise, currently around $76 per 1,000 kilometres for a light diesel; and there are the fixed costs of simply owning a vehicle, such as insurance, registration, warrant of fitness, servicing, tyres and depreciation, which you pay whether you drive 5,000 or 30,000 kilometres a year. This tool brings them together. You enter your fuel economy in litres per 100 kilometres and the fuel price, add road user charges if your vehicle pays them, and enter your yearly fixed costs along with the kilometres you drive in a year. It then shows your cost per kilometre broken into fuel, road user charges and fixed costs, both in cents per kilometre and as a total for the year. Seeing the number in cents per kilometre is genuinely useful: it helps you set a fair mileage reimbursement, decide whether a longer commute is worth it, compare a thirsty vehicle against an efficient one, or work out the true cost of a side gig that involves a lot of driving. Spreading fixed costs over your annual kilometres is what turns a fuel figure into a real running cost. The result is an estimate to guide budgeting and decisions, not an exact account.
For petrol leave RUC at zero (excise is in the pump price). Light diesel RUC is about $76 per 1,000km. An estimate for budgeting only.
Fuel cost per kilometre is your litres per 100 kilometres divided by 100, times the fuel price. Road user charges per kilometre are the RUC rate divided by 1,000. Fixed costs per kilometre are your yearly maintenance, tyres, insurance, registration and warrant divided by your annual kilometres. Adding the three gives the total cost per kilometre, and multiplying that by your annual kilometres gives the cost for the year.
A petrol car using 7.5 L/100km at $2.85 a litre costs 21.4 cents per kilometre in fuel, with no road user charges. With $1,500 of maintenance and tyres and $1,200 of insurance, rego and warrant over 12,000 kilometres a year, fixed costs add 22.5 cents per kilometre. The total is about 43.9 cents per kilometre, or roughly $5,265 a year. A light diesel would add about 7.6 cents per kilometre in road user charges.
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