Tire Size Calculator - Free Online Calculator
Thinking about different wheels or tyres? Compare their overall size and see how your speedometer and gearing will change.
- Formula shown on the page
- Runs in your browser
- Your inputs stay private
New overall diameter
645.2 mm
was 634.3 mm
Diameter change
1.72%
Real speed at 100 km/h indicated
101.7 km/h
Sidewall height (new)
94 mm
Revolutions per km (new)
493
The change is within the usual 3% tolerance.
Some content is still shown in English.
Understanding the Tire Size Calculator
Owning a vehicle in India involves more ongoing math than most buyers anticipate at the showroom. Road tax varies by state, insurance renewals go up each year, fuel prices shift weekly, and depreciation quietly erodes resale value in the background. The Tire Size Calculator puts the specific numbers in front of you using Indian-market defaults - the kind a generic international calculator would miss entirely.
Use the Tire Size Calculator to budget before buying, run a periodic cost check during ownership, or plan a road trip. For business-use vehicles where you're claiming expenses against tax, use the calculator's output as a starting figure and have your CA confirm what's deductible under the current rules - that part changes more often than the depreciation math does.
Using the Tire Size Calculator in 3 steps
Enter the current tyre's width, aspect ratio and rim size (for example 225/45 R17).
Enter the new tyre's numbers.
Check the diameter change and real speed.
How the Tire Size Calculator works
Overall diameter is the rim diameter plus two sidewalls, where each sidewall is the width times the aspect ratio. A larger diameter covers more ground per turn.
Diameter = rim x 25.4 + 2 x (width x aspect / 100)
- widthtyre width in mm
- aspectsidewall height as a percent of width
How the Tire Size Calculator gets its answer
The Tire Size Calculator uses Indian-specific defaults wherever relevant: petrol, diesel and CNG prices in major Indian cities, RTO rules for road tax, average vehicle insurance premiums, and standard fuel-economy figures published by ARAI.
Costs are estimates. Fuel prices change daily and vary by city; insurance premiums depend on the vehicle's IDV, your location and your claim history; depreciation curves differ by brand and segment. Use the Tire Size Calculator as a directional input and refine with quotes from dealers, insurers or fleet operators.
When to use the Tire Size Calculator
- Buyers comparing the all-in cost of two vehicles before making a purchase decision.
- Existing owners deciding when to sell or replace based on rising running costs.
- Trip planners estimating fuel and toll costs before a road trip.
- Fleet managers budgeting periodic maintenance and replacement cycles for a vehicle pool.
Common mistakes and gotchas
- Using a city's average fuel price for trip planning across multiple states. Diesel and petrol prices can vary by ₹3-5 per litre across states.
- Forgetting taxes and insurance in total ownership cost. Road tax (5-12%) and 5-year insurance can together add 10-15% to vehicle on-road price.
- Ignoring depreciation. A ₹15 lakh new car is worth ₹8-9 lakh after 5 years - that's roughly ₹1-1.4 lakh of depreciation per year, often more than fuel.
- Comparing only EMI between vehicle loan options. Down-payment, processing fee and total interest matter more than monthly EMI alone.
Get more out of this tool
- Always factor depreciation into your ownership cost - it's typically the biggest line item over 5+ years.
- Compare on-road price (not ex-showroom) when shopping. The difference is 10-20% and varies by state.
- Pair this calculator with the EMI and fuel-cost calculators for a complete picture of vehicle ownership economics.
- Re-run the trip-cost calculation periodically as fuel prices change - the same trip can cost 10% more or less month to month.
Questions about the Tire Size Calculator
What does 225/45 R17 mean?
225 mm wide, sidewall is 45% of the width, radial construction, 17 inch rim.
How much change is safe?
Keep overall diameter within about 3% of the original.
Total cost of ownership, simplified
Owning a vehicle in India means juggling EMI, fuel cost, depreciation, charging cost (for EVs), maintenance and trip cost. These numbers are interconnected - a longer commute means more fuel, faster depreciation, and bigger interest payments. Rather than treat them in isolation, the vehicle calculators help you see the full stack before you sign on the dotted line.
Pair this calculator with the EMI, depreciation, fuel cost and EV charging calculators to compute the realistic monthly cost of ownership. For depreciation we follow the IRDAI standard schedule used by Indian insurers for IDV (Insured Declared Value); for EV charging we model losses, charger type and time-of-use tariffs.
The Tire Size Calculator is part of the Vehicle suite on Online Calculator Tools, alongside 5 related calculators. All tools share the same UI patterns, the same privacy-first rendering (nothing is sent to a server), and the same commitment to showing the formula and assumptions behind every result.