AutoCalc Help Documentation

A complete guide to the car calculators and the garage log, from the price list to the next service.

Last Updated: November 9, 2026

Table of Contents

  1. Getting Started
  2. Units and Typing Values
  3. On-Road Price
  4. Car Loan
  5. Can You Afford It?
  6. The Cost of Owning
  7. What a Car Is Worth
  8. Trips and Running Costs
  9. Charging an Electric Car
  10. Mileage
  11. Tyre Sizes
  12. Reading a Sidewall
  13. Power and Performance
  14. Your Garage
  15. Settings and Your Data
  16. Keyboard Shortcuts
  17. How It Was Checked
  18. Troubleshooting
  19. Support

1. Getting Started

The six tabs choose the tool: Buying, Cost of owning, Trips and charging, Tyres, Power and Garage. Above them, the toolbar shows the units in use, with the km/L, L/100 km, US mpg and UK mpg switch, Settings and Help. Answers change as you type; there is nothing to press. Most tools offer an example to try when they are empty, such as Try an 8 lakh car; the example's figures are examples, to be replaced by yours.

On a computer the boxes are on the left and the answer on the right; on a phone the answer comes under the boxes, and a one-line summary stays at the top of the screen while you type.

2. Units and Typing Values

Choose the units in the toolbar, or press U to move to the next: kilometres and km a litre, kilometres and litres per 100 km, miles and US miles per gallon, or miles and UK miles per gallon. Every box you have typed in is converted. A box with a small list beside it takes the unit chosen there.

The line under each box shows what was understood (4.5 lakh), or says that the value cannot be read.

3. On-Road Price

  1. Type the Ex-showroom price from the dealer's price list. It already includes GST.
  2. Type the Road tax as a percent of the ex-showroom price. Your state sets it, often by fuel and price band, and many states charge less or nothing for electric cars, so the box starts empty.
  3. Type Registration and plates and Insurance, first year (ask for quotes; it is often cheaper outside the dealer).
  4. With rupees, TCS of 1% is added on a car priced over 10 lakh (Over 10 lakh), always (Add) or never (Leave out).
  5. Under Extras and discounts, add FASTag, accessories, an extended warranty and other charges (ask what each is for), and take off cash, exchange, corporate and festive discounts together.

The answer shows the on-road price, how much it is over the ex-showroom price, a bar of where the money goes and each line. TCS is not a cost: the dealer deposits it against your PAN as tax already paid, and it comes back against your income tax. Share copies the price and the loan to send, and Print prints them on one sheet.

4. Car Loan

  1. Under Loan amount, choose On-road price less down payment (type the down payment as a share such as 20% or an amount such as 2L) or Type it.
  2. Type the Interest rate you were quoted and choose Reducing or Flat. The box starts empty and is never taken as 0%.
  3. Type how long the loan runs in Years or Months (up to 50 years), and the Processing fee if there is one.
  4. Under Part payments, add an extra amount each month (from a month you choose), each year (paid with every twelfth EMI) or one payment in a month you choose.

The EMI uses the reducing-balance method banks use. The answer shows the interest, the real rate behind a flat rate (or what a flat-rate quote would need to match), the real cost with the fee, what the car costs you in all, a chart of what you still owe month by month and a table year by year. With part payments, the EMI stays the same, the loan ends sooner, and the months and interest saved are shown. Under the RBI's rules a floating-rate loan to a person for personal use carries no part payment charges; check your own loan's terms.

5. Can You Afford It?

Type your Monthly income before tax (add a partner's income if you share the car) and your Running costs a month (fuel, insurance, service and parking; the Cost of owning tab works these out). AutoCalc checks the price and the loan against the 20/4/10 rule, a common rule of thumb: at least 20% down, at most 4 years, and the EMI and running costs under 10% of your income. It also shows the most expensive car the rule allows: the on-road price with 20% down over 4 years at your interest rate, keeping the EMI within what is left of the 10%.

6. The Cost of Owning

  1. Type how far You drive a year, how long you Keep it for, a yearly rise in fuel prices if you expect one, and, if you like, a Cab fare a km to compare with not owning a car.
  2. For your car, type its name, fuel, On-road price, Real mileage, the fuel or electricity price, Insurance a year and Service a year (with tyres and repairs).
  3. Type the Value lost in year 1 and in Each year after, as a percent, or under Loan and resale the Resale price you expect when you sell it. Used-car listings for your model are the best guide. Until you type one of them, the value lost is not counted and the page says so.
  4. Under Loan and resale, type the share of the price borrowed, the rate and how long the loan runs, to count its interest.
  5. Add a car to compare adds a second and a third car, or start from an example: Petrol or electric, Petrol or CNG or Petrol or diesel.

One car: the cost a km and a month, what it is worth at the end, a bar of where the money goes and a chart of the cost so far. Several cars: which is cheapest over the years and distance with resale counted, whether and when the dearer one pays back its higher price in lower running costs, a chart of the money spent so far on each, and a table of every cost.

7. What a Car Is Worth

Type the Ex-showroom price when new and the Age in years. The insured declared value (IDV) follows the India Motor Tariff's table: the maker's listed price less 5% up to 6 months, 15% up to a year, 20% up to two years, then 30, 40 and 50% up to five; after five years it is agreed between you and the insurer. Type the value lost in the first year and in each year after to see the market value today, in a year, on a chart and in a table year by year.

8. Trips and Running Costs

Under Trip cost, choose the fuel and type where you are going (optional), the Distance one way (tick Round trip to double it), your Real mileage, the fuel price, Tolls one way (with Pay the tolls both ways on a round trip) and the People sharing. Under Parking, food and stops, add shared costs and the tank size (for an electric car, the usable battery and the charge at the start) to count the stops: a refill when about 10% is left, or a charge from 10 to 80%. The answer shows the total, each person's share, the cost a km, the stops, the range and the CO2. Share the split copies it to send. If the garage knows your car's mileage, a button fills it in.

Under Every month, type how far you drive each day, week or month, your mileage and the price, for the cost a month, a year and a km, what one more rupee a litre adds in a year, and what 10% better mileage saves.

CO2 is from burning the fuel: petrol 2.35 kg a litre and diesel 2.69 kg (the US EPA's figures for a gallon, 8,887 g and 10,180 g), CNG 2.75 kg a kg (counted as methane), and for electricity India's grid average for 2025-26, 0.675 kg a kWh (Central Electricity Authority, CO2 Baseline Database version 22.0).

9. Charging an Electric Car

  1. Under Charging, type the Usable battery in kWh (a little under the gross size in the brochure) and what the car Uses, for the range added.
  2. Type the Charge now and Charge to percentages and choose the Charger, from a 3.3 kW home socket to a 180 kW fast charger, or Other power.
  3. Type what the car takes on AC (its onboard charger) and on DC (its top fast-charging power), the Price a kWh from your bill or the charger, any session fee, and the charging efficiency if you know it.

Home charging (AC) runs at the lower of the charger's and the car's power until nearly full; fast charging (DC) slows after about half full and crawls above 80%, so the time to 80% is shown separately. The times are estimates from typical charging curves, assuming 88% of the electricity reaches the battery on AC and 93% on DC unless you type your own figure. The table shows the same charge on every kind of charger.

10. Mileage

Under Mileage, From a fill-up: fill to full, drive, fill to full again, and type the distance driven and what the second fill took. Convert turns any mileage into every unit for its fuel. To follow your mileage over months, log every fill-up in the Garage.

11. Tyre Sizes

Type the size Now on the car (on the tyre's side and on a sticker in the driver's door frame) and the New size, or pick one of the common sizes; the swap button exchanges them. Metric sizes (205/55 R16), American P and LT sizes, inch sizes (31x10.50R15) and old sizes without a sidewall figure (185R14, taken as 82%) are read. The answer gives the change in diameter with a verdict (within 3% is usually fine, 3 to 5% needs care, more than 5% is not advised), what the car does when the speedometer shows 100, how much higher or lower it sits, both tyres drawn to scale, a table of width, sidewall, rim, diameter, circumference and turns a km, the real speed for each speedometer reading, and what to check. Other sizes that fit lists sizes within 1, 2 or 3% of the diameter on the same rim and the ones around it; press one to compare it.

12. Reading a Sidewall

Under Read a sidewall, type the size with its load and speed marks (205/55 R16 91V XL), the last four digits of the DOT code and, if you like, the tread depth. Each mark is explained: the width, the sidewall, the construction, the rim, the load index (the kg each tyre carries at full pressure, from the standard table), the speed rating (Z and (Y) mean over 240 and over 300 km/h), XL, RF and C. The DOT digits give the week and year it was made and its age: Michelin advises a yearly check from 5 years old, and tyre makers advise replacing tyres 10 years after they were made at the latest (some car makers say 6). For the tread, 1.6 mm is the legal minimum in many countries, and Continental advises replacing at 3 mm for grip on wet roads.

13. Power and Performance

14. Your Garage

  1. Press Add your vehicle (or Look at an example to look around first). Type its name, whether it is a car or a two-wheeler, the fuel, the odometer, the tank size, the registration number, the tyre size and, if you know them, the date and odometer of the last service.
  2. After each visit to the pump, press Add fill-up: the date, the odometer, any two of the amount, the price and the total (the third is worked out), and tick Full tank when you fill to the top. If you forgot one, tick I missed logging the last fill-up on the next.
  3. Press Service or expense to log a service, a repair, tyres, insurance, parking, tolls and so on. Tick the reminders done on a service visit to start them counting again.

The garage shows the real mileage (full tank to full tank), the fuel cost a km, the spending this year, how far you drive a month, and what needs attention. Service reminders come due by distance or time, whichever comes first, with the date for the distance worked out from how far you drive; a new vehicle starts with example intervals for its fuel, to change to your owner's manual. Papers warn 30 days before they run out, and Renewed moves the date on. Add the due dates to a calendar saves a calendar file with an alert three days before each date. Mileage and spending charts each full tank and the last 12 months. The Log lists every entry (press the pencil to change one), with Spreadsheet to save it and Import to read a CSV file. Quick checks such as tyre pressure and lights come round again when they are due.

In India a new vehicle needs no pollution certificate in its first year; after that a certificate lasts a year for BS-IV and BS-VI vehicles and six months for older ones. A private car's registration lasts 15 years and is then renewed for 5 years at a time.

15. Settings and Your Data

Settings holds the units and the money sign (rupee, dollar, pound, euro, dirham or none; rupees also show lakh and crore, and the TCS line when buying). Under Your data: Save a backup writes everything to a file, Open a backup replaces what is here with a backup after you confirm (files over 10 MB are refused, and every value is checked), and Delete everything removes AutoCalc's data from this browser and leaves the rest of the site alone. Everything is kept in this browser on this device; nothing is written until you type or choose something. The site's sun and moon button sets the light or dark theme.

16. Keyboard Shortcuts

Outside a text box: 1 to 6 open the six tools, U moves to the next units, and ? opens the help. On the tabs, ← and → move between them, with Home and End; on a chart, they read the values one by one. Esc closes a window. A link to the tool ending in #own, #trip, #tyres, #power or #garage opens that tool.

17. How It Was Checked

Before it was published, the figures the tool states were checked against their sources: the 1% TCS on vehicles over 10 lakh, the IDV table of the India Motor Tariff, the standard load index and speed rating tables, the US EPA's CO2 figures for petrol and diesel, the Central Electricity Authority's grid figure, the rules for pollution certificates and registration, the standard test for run-flat tyres, and the tyre makers' advice on age and tread. Figures with no reliable source (fuel prices, road tax, interest rates, how fast a car loses value) are left for you to type. Its sums were then compared with a separate reference written from the rules on this page, with tens of thousands of cases: amounts written in many ways, every unit of mileage, on-road prices, loans with flat rates, fees and part payments, the 20/4/10 check, the cost of owning with and without resale figures, payback, the IDV by age, trips and stops, charging times, tyre sizes parsed and compared against a search of every size, gears and engine sizes, the garage log's mileage and reminders against an independent date library, the calendar file, spreadsheets, and damaged and hostile values. The page was then checked in the browser on phones and computers, in both themes, with an accessibility scan of every tool and window.

18. Troubleshooting

19. Support

For questions the FAQ does not answer, use the contact form. These tools are for planning; check prices, taxes and service intervals with your dealer, insurer, lender and owner's manual.