Automotive Calculators
From fuel costs and MPG to car loans and EV vs petrol comparisons — our free automotive calculators help you understand the true cost of owning and running a vehicle.
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Fuel & Running Costs
Fuel cost per mile, MPG, and trip cost calculators
Buying & Financing
Car loan, lease vs buy, and total cost of ownership
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Automotive Glossary — Key Terms Explained
- MPG (Miles Per Gallon)
- Fuel efficiency measure: miles driven ÷ gallons consumed. US uses US gallons (3.785 litres). UK uses Imperial gallons (4.546 litres) — UK MPG figures are always higher than US MPG for the same car due to larger gallon size.
- L/100km
- Litres per 100 kilometres — the EU/metric fuel efficiency measure. Lower = more efficient. Conversion: L/100km = 282.5 ÷ MPG (UK) or 235.2 ÷ MPG (US).
- Cost Per Mile / Per Km
- Total running cost divided by distance. Includes fuel, insurance, servicing, tyres, and depreciation. Most driver's underestimate total cost per mile — the RAC estimates 40–70p per mile for a typical family car in the UK when all costs are included.
- Depreciation
- The reduction in car value over time. A new car loses 15–35% of its value in the first year and 50–60% within 3 years. Depreciation is typically the single largest cost of car ownership for new vehicles.
- APR (Auto Finance)
- Annual Percentage Rate — the true cost of car finance including interest and fees. Always compare car finance using APR, not just monthly payment. A longer term with lower monthly payments often means significantly more total interest paid.
Frequently Asked Questions
How do I calculate my fuel cost for a trip?
Fuel cost = (Distance ÷ Fuel efficiency) × Fuel price. Example: 200-mile trip in a car doing 35 MPG at £1.50/litre: 200 ÷ 35 = 5.71 gallons × 4.546 litres/gallon = 26 litres × £1.50 = £39. For a quick estimate, divide distance by MPG in UK gallons × current price per gallon.
Is it cheaper to lease or buy a car?
Leasing: lower monthly payments, always driving a new car, no depreciation risk — but you never own the car and pay more long-term. Buying outright or financing: higher initial cost but you own the asset. For high-depreciation premium cars, leasing can be cheaper overall. For reliable mainstream cars held 5+ years, buying wins on total cost.
How do I calculate MPG?
Fill up fully, zero the trip meter, drive normally, fill up again. MPG = Miles driven ÷ Gallons used. Example: filled up after 350 miles and used 12 gallons: 350 ÷ 12 = 29.2 MPG. For litres: convert using 1 UK gallon = 4.546 litres.
What is the true cost of owning a car?
Beyond the monthly payment, car ownership includes: insurance (£600–£2,000/year), road tax (£0–£580/year depending on emissions), MOT/service (£300–£600/year), fuel (£1,000–£2,500/year for typical driver), tyres (£200–£500/year amortised), and depreciation (£1,000–£5,000/year). Total: £3,000–£12,000/year depending on car and usage.