Automotive Calculators
Car depreciation, fuel economy, tire size & lease vs buy calculators.
What Are Automotive Calculators?
Automotive calculators help car buyers, owners, and fleet managers make informed decisions about vehicle costs, fuel economy, financing, and depreciation. Owning or running a vehicle involves significant ongoing costs beyond the purchase price — fuel, insurance, maintenance, road tax, and depreciation — and these calculators make the full picture visible before and after purchase.
Car depreciation calculators estimate how much a vehicle will lose in value over time. Depreciation is the largest single cost of car ownership for most drivers, yet it is the least visible because no cash changes hands. New cars typically lose 15–25% of their value in the first year and 50–60% over three years. Some makes and models hold their value far better than others, and understanding residual values is crucial for both buyers and fleet managers.
Fuel cost and economy calculators compare the running cost of different vehicles and fuel types — petrol, diesel, hybrid, and electric. Fuel economy is measured in miles per gallon (mpg) in the UK and US, or litres per 100 km (L/100km) in Europe and most other countries. Our calculators convert between these formats and estimate the annual fuel cost based on your typical annual mileage.
Car loan and lease calculators reveal the true cost of financing a vehicle. Car loan calculators apply the standard EMI formula to show monthly payment, total interest paid, and total cost of ownership over the loan term. Lease vs buy calculators compare the total cost of leasing (fixed monthly payments, no asset at the end) against buying (higher monthly cost, equity built up). For drivers who change cars every 3–4 years, leasing is often cheaper; for those who keep cars long-term, buying wins.
Vehicle ownership cost calculators aggregate all costs — purchase price (or lease payments), fuel, insurance, maintenance, road tax, tyres, and depreciation — into a total cost per mile or per year. This comprehensive view enables fair comparisons between vehicles that have different purchase prices, fuel economies, and reliability profiles.
All Automotive Calculators (7)
Car Depreciation Calculator
Calculate how much your car depreciates each year and its future resale value.
Vehicle Loan Affordability Calculator
Calculate the maximum car price you can afford based on income, down payment, and loan terms.
Tire Size Calculator
Compare tire sizes, calculate speedometer error, and find equivalent tire options.
EV Range Calculator
Calculate electric vehicle range based on battery capacity, efficiency, and driving conditions.
Fuel Economy Calculator
Calculate fuel economy (MPG/L per 100km), fuel cost per mile, and annual fuel spend.
Road Trip Fuel Calculator
Calculate fuel cost for any road trip based on distance, MPG, and fuel price.
Lease vs Buy Car Calculator
Compare total cost of leasing vs buying a car over any ownership period.
Automotive Calculator Guides
Depreciation & Ownership Costs
Car depreciation follows a declining balance pattern: the percentage lost is roughly constant each year, applied to the current value rather than the original price. A typical 20% annual depreciation rate: Year 1: £20,000 × 0.8 = £16,000 (lost £4,000); Year 2: £16,000 × 0.8 = £12,800 (lost £3,200); Year 3: £12,800 × 0.8 = £10,240 (lost £2,560). After 3 years, 49% of original value remains — but some models retain 55–65% and others only 30–35%.
Total cost of ownership per mile = (Purchase Price − Residual Value + Fuel + Insurance + Maintenance + Tax + Financing Interest) ÷ Total Miles Driven. For a car driven 10,000 miles/year for 4 years, total miles = 40,000. Dividing all four-year costs by 40,000 gives a true pence-per-mile figure that enables honest comparisons between cheap-to-buy, expensive-to-run vehicles and expensive-to-buy, cheap-to-run alternatives.
Fuel Economy & Running Costs
Fuel cost per mile: Petrol/Diesel: (Fuel Price per Litre × 4.546) ÷ MPG; or in metric: L/100km × Fuel Price per Litre ÷ 100. For a car doing 40 mpg at 150p/litre: (150 × 4.546) ÷ 40 = 17.05p/mile. An EV at 4 miles/kWh charged at 7p/kWh: 7 ÷ 4 = 1.75p/mile — approximately 10× cheaper per mile than the petrol example.
Converting between mpg and L/100km: L/100km = 282.5 ÷ mpg (UK); L/100km = 235.2 ÷ mpg (US). Note that UK and US gallons differ (1 UK gallon = 4.546 L; 1 US gallon = 3.785 L), so UK and US mpg figures are not directly comparable. A car quoted at 50 mpg UK is only 41.6 mpg US.
Car Loans & Lease vs Buy
Car loan monthly payment uses the standard EMI formula: PMT = P × r × (1+r)^n ÷ [(1+r)^n − 1]. A £15,000 loan at 6.9% APR over 48 months: monthly rate r = 6.9%/12 = 0.575%; PMT = 15,000 × 0.00575 × (1.00575)^48 ÷ [(1.00575)^48 − 1] = approximately £355/month. Total repaid: £355 × 48 = £17,040 — £2,040 in interest.
Lease vs buy: leasing suits drivers who change cars every 2–4 years, want to avoid depreciation risk, and prefer fixed monthly costs. Buying suits drivers who keep cars for 6–10 years and want to own the asset. In the lease vs buy comparison, the key metric is total cash out over the ownership/lease period — factoring in down payment, monthly payments, and the equity position (residual value) at the end.
Top Automotive Calculators
Car Depreciation Calculator
Estimate how much your car will be worth in 1, 3, or 5 years using declining-balance depreciation.
Car Loan Calculator
Calculate monthly car loan payments and total interest for any loan amount, rate, and term.
Fuel Cost Calculator
Estimate the fuel cost of any trip given distance, fuel economy, and current pump price.
Lease vs Buy Car Calculator
Compare the total cost of leasing versus buying a car over any ownership horizon.
Fuel Economy Calculator
Calculate MPG or L/100km from fill-up data and compare fuel efficiency across vehicles.
Key Formulas & References
Depreciation (declining balance)
Value after n years = P × (1 − r)^n
P = purchase price, r = annual depreciation rate (e.g. 0.20 for 20%)
Fuel Cost per Mile (UK)
(Fuel Price p/litre × 4.546) ÷ MPG
Result in pence per mile; 4.546 = litres per UK gallon
MPG to L/100km
L/100km = 282.5 ÷ UK MPG
For US MPG: L/100km = 235.2 ÷ US MPG
Car Loan PMT
P × r × (1+r)^n ÷ [(1+r)^n − 1]
P = principal, r = monthly rate (APR÷12), n = months
Frequently Asked Questions About Automotive Calculators
Average depreciation is approximately 15–25% of current value per year, though it varies significantly by make, model, and condition. New cars lose the most in year 1 (15–25%); the rate typically slows after year 3. Some models (certain Toyota and Honda vehicles) retain 55–65% of their value after 3 years; luxury and high-volume models may retain only 30–40%.
L/100km = 282.5 ÷ UK MPG (or 235.2 ÷ US MPG). Reverse: UK MPG = 282.5 ÷ L/100km. Note that UK and US gallons differ — 1 UK gallon = 4.546 L vs 1 US gallon = 3.785 L — so UK and US MPG figures cannot be directly compared without conversion.
Leasing is typically cheaper over short periods (2–4 years) because monthly payments are based on depreciation during the lease term, not the full vehicle price. Buying becomes cheaper over longer periods because depreciation slows and ownership costs reduce. Buying is also better if you drive high mileage (excess mileage charges apply to leases) or want to own an asset.
Car loan PMT = P × r × (1+r)^n ÷ [(1+r)^n − 1], where P = loan amount, r = monthly interest rate (APR ÷ 12), n = loan term in months. This is the standard amortisation formula. The total interest paid = (PMT × n) − P. Our car loan calculator shows the full amortisation schedule so you can see the interest/principal split each month.
Total Cost of Ownership = Depreciation + Fuel + Insurance + Road Tax + Maintenance & Tyres + Financing Interest + Parking. For a typical mid-range car driven 10,000 miles/year in the UK, total annual cost is approximately £4,000–£7,000 including depreciation. Our vehicle cost calculator aggregates all these components to give a cost per mile and per year.
Fuel Cost = (Distance ÷ MPG) × Price per Gallon, or (Distance × L/100km ÷ 100) × Price per Litre. In metric: a 500 km trip in a car doing 7 L/100km at 1.55 €/L costs (500 × 7 ÷ 100) × 1.55 = 35 × 1.55 = £54.25 in fuel. Add a buffer for motorway speeds (typically 15–20% higher fuel consumption than combined cycle).
BrainyCalculators Editorial Team
Our Automotive calculators are researched, built, and reviewed by the BrainyCalculators editorial team using industry-standard formulas and validated against authoritative references. Results are updated whenever underlying standards, rates, or guidelines change. All calculators are free, require no account, and run entirely in your browser.