Tyres, running costs, tax, insurance and EV charging, worked out from official rules
These free automotive tools help you buy, run and look after a car or bike, in your browser and with nothing sent anywhere. For tyres, the tyre size calculator compares two sizes with a scale drawing and speedometer error, the load index and speed rating chart decodes the service description, and the tyre DOT code decoder tells you when a tyre was made. The bike tyre pressure calculator uses the tyre-drop method for bicycles.
For costs, the cost per km calculator adds fuel, service, insurance and depreciation, the car depreciation calculator shows the value over time, and the CC to HP estimator and engine displacement and compression ratio calculator cover the engine. Electric car owners have the EV charging cost calculator, the EV charging time calculator and the EV range calculator.
For paperwork in India, the road tax calculator uses each state's notified rates, the RTO code list finds any registration code, the IDV calculator follows the motor tariff depreciation table, the no claim bonus calculator shows your discount, and the third-party insurance premium chart lists the IRDAI rates. In the UK, the UK car tax calculator works out vehicle tax from GOV.UK's rate tables, and the VIN decoder checks any 17-character VIN offline.
Where the numbers come from
- Official rules, dated. Road tax comes from state motor vehicle tax acts and notifications, insurance figures from IRDAI and the India Motor Tariff, and UK vehicle tax from GOV.UK. Each page names its source and the date it was checked. Where a rate could not be confirmed, the tool asks you to enter it.
- Estimates are labelled. Horsepower from engine size, depreciation, EV range and charging slow-down are models, and the pages say so. Your vehicle maker's figures and your insurer's quote come first.
Related tools elsewhere on the site
- Fuel and loans. The fuel cost calculator and mileage calculator are in the productivity sector, and the car loan calculator is in finance.
- Gears and trucks. The gear ratio calculator is in science and engineering, and the truck cost per mile calculator is in e-commerce and shipping.
Automotive & Vehicles: frequently asked questions
Are these car calculators free?
Yes. They are free, need no account and run in your browser. Your VIN, number plate and costs are not sent anywhere.
Can I fit a different tyre size?
Many fitters keep the new overall diameter within about 3% of the original, but that is a guideline, not a law. Your vehicle maker’s approved sizes, load index and speed rating come first. The tyre size calculator shows the difference and the speedometer error.
How is IDV calculated for car insurance in India?
IDV is the ex-showroom price minus depreciation for the vehicle’s age under the India Motor Tariff: 5% up to 6 months, 15% up to 1 year, then 20%, 30%, 40% and 50% up to 5 years. Over 5 years, IDV is agreed between you and the insurer.
How do I read a tyre DOT code?
The last four digits give the week and year of manufacture, so 2321 means week 23 of 2021. The letters after DOT identify the factory. The DOT code decoder shows both and the tyre’s age today.
How long does an electric car take to charge?
Divide the energy you need by the charging power, after allowing for losses, and remember that fast charging slows above about 80%. The EV charging time calculator does this for home sockets, wallboxes and DC chargers.