People choose a car on the sticker price and the monthly payment, then pay for it for years in depreciation, finance interest, insurance, tax, servicing, tyres and fuel. Paste up to four vehicles — petrol, diesel, electric or plug-in hybrid, mixed freely — and this compares them on the total over a period you choose, with the cost per year, per month and per mile or kilometre, and a full itemised breakdown whose lines sum exactly to the total. Efficiency can be given in mpg (US or imperial gallon — they are different volumes and the tool will not guess), L/100km, km/L, mi/kWh, km/kWh or kWh/100km, and the conversions are exact. Nothing about the world is built in: not a fuel price, not an electricity price, not an insurance premium, not a tax figure, not a servicing cost, not a depreciation rate and not an efficiency figure for any vehicle, because every one of those differs by country, year, driver and vehicle. The answer is only as good as your resale estimate, which is the largest and least certain number in it. No vehicle is recommended; the list is ranked by total cost and stops there. This is not financial advice.
Worked example
CAR TOTAL COST OF OWNERSHIP — 3 vehicles over 5 years, 10,000 miles a year (50,000 miles in total)
Every figure below comes only from the numbers you pasted. No fuel price, electricity price, insurance premium, tax, servicing cost, depreciation rate or efficiency figure is built into this tool.
Small petrol car
$20,000.00 price, $8,000.00 deposit, $12,000.00 borrowed at 0.00% over 24 months.
Monthly payment $500.00 · final payment $500.00 settles the balance to exactly $0.00.
Depreciation $12,000.00 (purchase $20,000.00 − your resale estimate $8,000.00)
Finance cost $0.00 ($12,000.00 paid over the term − $12,000.00 borrowed)
Insurance $3,000.00 ($600.00 a year × 5 years)
Road tax / registration $1,000.00 ($200.00 a year × 5 years)
Servicing & maintenance $2,000.00 ($400.00 a year × 5 years)
Tyres $1,000.00 ($200.00 a year × 5 years)
Fuel / electricity $7,273.74 (50,000 miles at 50 mpg (imperial gallon) = 4,546.09 litres at $1.6000 per litre → $7,273.74)
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TOTAL over 5 years $26,273.74
Cost per year $5,254.75
Cost per month $437.90
Cost per mile $0.5255
Largest single cost: Depreciation — $12,000.00 of the $26,273.74 total (45.7%)
Small electric car
Bought for $30,000.00 outright — no finance.
Depreciation $18,000.00 (purchase $30,000.00 − your resale estimate $12,000.00)
Finance cost $0.00 (no finance — nothing borrowed)
Insurance $3,500.00 ($700.00 a year × 5 years)
Road tax / registration $0.00 ($0.00 a year × 5 years)
Servicing & maintenance $1,000.00 ($200.00 a year × 5 years)
Tyres $1,250.00 ($250.00 a year × 5 years)
Fuel / electricity $3,750.00 (50,000 miles at 4 mi/kWh = 12,500.00 kWh at $0.3000 per kWh → $3,750.00)
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TOTAL over 5 years $27,500.00
Cost per year $5,500.00
Cost per month $458.33
Cost per mile $0.5500
Largest single cost: Depreciation — $18,000.00 of the $27,500.00 total (65.5%)
Older used car
Bought for $9,000.00 outright — no finance.
Depreciation $5,000.00 (purchase $9,000.00 − your resale estimate $4,000.00)
Finance cost $0.00 (no finance — nothing borrowed)
Insurance $2,750.00 ($550.00 a year × 5 years)
Road tax / registration $1,000.00 ($200.00 a year × 5 years)
Servicing & maintenance $2,500.00 ($500.00 a year × 5 years)
Tyres $1,000.00 ($200.00 a year × 5 years)
Fuel / electricity $9,092.18 (50,000 miles at 40 mpg (imperial gallon) = 5,682.61 litres at $1.6000 per litre → $9,092.18)
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TOTAL over 5 years $21,342.18
Cost per year $4,268.44
Cost per month $355.70
Cost per mile $0.4268
Largest single cost: Fuel / electricity — $9,092.18 of the $21,342.18 total (42.6%)
SIDE BY SIDE — over 5 years
vehicle total per year per month per mile vs cheapest
Older used car $21,342.18 $4,268.44 $355.70 $0.4268 cheapest
Small petrol car $26,273.74 $5,254.75 $437.90 $0.5255 +$4,931.56
Small electric car $27,500.00 $5,500.00 $458.33 $0.5500 +$6,157.82
WHAT DOMINATES EACH ONE
Older used car Fuel / electricity — $9,092.18 (42.6%)
Small petrol car Depreciation — $12,000.00 (45.7%)
Small electric car Depreciation — $18,000.00 (65.5%)
For most vehicles the largest line is depreciation, not fuel. That is usually the surprise, and it is why the resale estimate matters more than the pump price.
NOTES
· The resale estimate is yours. It is the largest and least certain number in this comparison, and the whole answer is only as good as it is. This tool does not supply one, does not look one up, and does not apply a depreciation curve — if your estimate is out by a few thousand, so is every total above.
· Depreciation is simply purchase price minus your resale estimate, spread across the period. No curve is assumed.
· Finance cost is the total actually paid over the whole term minus the amount borrowed, worked out with a real month-by-month amortisation in whole cents. If the term runs past the comparison period, the full term's interest is still counted, because you still owe it.
· Conversions are exact: 1 mile = 1.609344 km; 1 US gallon = 3.785411784 litres; 1 imperial gallon = 4.54609 litres. The US and imperial gallon differ by about 20%, so "mpg" on its own is refused — write mpg-us or mpg-uk.
· Fuel quantities are carried to a millionth of a litre or kWh and money is carried in whole cents throughout, so each itemised line sums exactly to the total shown.
· Not included: parking, tolls, cleaning, breakdown cover, fines, the cost of charging equipment, and the interest you would have earned on a cash purchase. Add them to the servicing field if you want them counted.
· No vehicle is recommended here. The list is ranked by total cost over the period you entered and nothing more. This is not financial advice.
Frequently asked
Can it compare a petrol car with an electric one?
Yes — that is the main thing it is for. Give each vehicle its own efficiency figure in its own unit (mpg-uk, mpg-us, L/100km, km/L, mi/kWh, km/kWh or kWh/100km) and its own energy price, and everything is converted internally and compared on the same total. A plug-in hybrid can carry two energy sources on one line, with you stating what share of the distance runs on each.
Why does it ask which gallon?
Because the US gallon is exactly 3.785411784 litres and the imperial gallon is exactly 4.54609 litres — about 20% larger. A figure of "50 mpg" therefore describes two noticeably different cars depending on which side of the Atlantic wrote it. Guessing would silently change the answer, so the unit is yours to state: mpg-us or mpg-uk.
Where does the resale value come from?
From you. This tool does not supply one and does not apply a depreciation curve, because resale values depend on the model, the mileage, the condition, the year and the local market, and they move constantly. It is also the single largest and least certain number in the comparison, so the honest thing is to make you own it — and to try a pessimistic and an optimistic figure and see how much the ranking moves.
How is the finance cost worked out?
As a real amortisation, month by month in whole cents: the level payment is the smallest number of cents that clears the balance inside the term, and the finance cost is the total actually paid minus the amount borrowed. It is not rate x balance x years, which overstates the cost badly on an amortising loan. Write "cash" in the rate field for an outright purchase and the finance cost is exactly zero.
Why is depreciation usually the biggest line?
Because it is the difference between what you paid and what the vehicle is worth when you sell, and on a newer car that is often larger than several years of fuel put together. It does not arrive as a monthly bill, so it is easy to miss — which is exactly why the tool names the largest line for every vehicle instead of leaving you to add up the column.
Which car should I buy?
This tool does not say. It ranks by total cost over the period you entered and stops. It knows nothing about what the vehicle needs to do, how long you will really keep it, what your resale estimate is worth, or anything it does not model — parking, tolls, breakdown cover, charging equipment. That judgement is yours.
Are the numbers on this page real?
No. They are an invented example so the page can show a working calculation. They are not typical, benchmark or recommended figures, and no make, model or brand is named anywhere in this tool. Replace every one of them with your own quotes and prices.