AutoCalc FAQ

Questions and answers about the car calculators and the garage log. Everything they work out happens in your browser.

Last Updated: November 9, 2026

1. General Questions

Q1: What is AutoCalc?

A1: Six tools for buying, running and looking after a car or a bike: the on-road price and the car loan, the cost of owning one car or comparing several, trips, fuel and electric car charging, tyre sizes, power and performance, and a garage log for your real mileage, spending, service reminders and papers. Answers change as you type, and each one shows how it is worked out.

Q2: How much does it cost?

A2: Nothing. It is free, with no registration and no limit. Like every page on ZeroDataUpload, it is supported by advertising.

Q3: Do I need to install anything or create an account?

A3: No. Open the page in any modern browser (Chrome, Edge, Firefox, Safari or Opera) on a computer, tablet or phone. What you type is kept in that browser, so there is nothing to sign in to.

Q4: Is anything I type uploaded?

A4: No. Prices, distances and your garage log are worked out by this browser on your device and never sent to a server. The page itself loads the site's ads and analytics, as every page on the site does; the Privacy Policy explains those, and your figures are never part of them.

Q5: Who is it for?

A5: Anyone buying a car who wants to know the real price and loan before visiting the dealer; anyone choosing between petrol, diesel, CNG and electric; anyone planning a road trip or charging an electric car; and anyone who wants to know their real mileage and never miss a service, an insurance renewal or a pollution certificate.

Q6: Does it work for bikes and for other countries?

A6: Yes. The garage takes cars and two-wheelers, with examples of a two-wheeler's service intervals. The units switch takes kilometres or miles and km a litre, litres per 100 km or US or UK miles per gallon, and Settings sets the money to rupees, dollars, pounds, euros, dirhams or no sign. The TCS line and the lakh and crore figures appear only with rupees.

2. Typing Numbers and Units

Q7: How do I type amounts?

A7: As 450000, 4,50,000, 4.5L, 4.5 lakh, 450k, 1.2 cr or Rs 4,500, and sums work too: 450 + 300 or 150 x 22. Under each box the amount is read back in words, such as 4.5 lakh, or the box says it cannot read what you typed. Amounts over 10 lakh crore are refused.

Q8: What do the small lists beside some boxes do?

A8: They set the unit of that one box: km or miles for a distance, km/L, L/100 km or mpg for mileage, a litre or a gallon for a price, kg or lb for weight, PS, bhp, hp or kW for power. So you can type miles in one box and kilometres in another.

Q9: What happens when I change the units?

A9: Choose km/L, L/100 km, US mpg or UK mpg at the top of the tool, or press U to move to the next. Every box you have typed in that uses the old unit is converted, to five significant figures, so switching there and back gives the number you typed.

3. Buying a Car

Q10: How is the on-road price worked out?

A10: The ex-showroom price, which already includes GST, plus road tax, registration and number plates, the first year's insurance, the TCS on a car over 10 lakh, FASTag, accessories, an extended warranty and other charges, less discounts. AutoCalc shows each line, its share of the total, and how much more than the ex-showroom price you pay.

Q11: What is TCS, and do I get it back?

A11: Tax collected at source: on a motor vehicle priced over 10 lakh, the dealer collects 1% of the price and deposits it against your PAN. It is not a cost: it counts as tax you have already paid, shows in your tax statement and reduces the tax you pay, or comes back as a refund when you file your return. A car of exactly 10 lakh has none.

Q12: Why do I have to type the road tax?

A12: Each state sets its own road tax, often by fuel and price band, and many charge less or nothing for electric cars. No single figure is right everywhere, so the box starts empty; your dealer's price breakup or your state's transport department has your rate. The examples fill in 10% as an example only.

Q13: What is the difference between a flat rate and a reducing rate?

A13: A reducing rate charges each month's interest on what you still owe, so the interest falls as you repay; banks quote car loans this way. A flat rate charges interest on the whole loan for the whole time. Choose Flat and AutoCalc shows the reducing rate that gives the same EMI: a flat 7% over five years is a reducing 12.5%.

Q14: Why does AutoCalc not fill in an interest rate?

A14: Rates differ by lender, by your credit history and from month to month, so the box starts empty and the EMI appears once you type the rate you were quoted. An empty box is never taken as 0%.

Q15: How does a processing fee change the cost?

A15: You pay the EMI on the whole loan but receive the loan less the fee, so the real rate is higher than the quoted one. AutoCalc shows it as the real cost with the fee: the rate at which the money you actually receive buys the same EMI.

Q16: How do part payments work?

A16: Under Part payments, add an extra amount each month, each year (paid with every twelfth EMI, such as from a bonus) or a single payment in a month you choose. The EMI stays the same and the loan ends sooner; AutoCalc shows the months saved and the interest saved. 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.

Q17: What is the 20/4/10 rule?

A17: A common rule of thumb, not a law or a lender's rule: pay at least 20% down, borrow for at most 4 years, and keep the EMI and running costs under 10% of your monthly income before tax. Type your income to see whether the car and the loan pass, and the most expensive car the rule allows at your interest rate.

4. The Cost of Owning

Q18: What does the cost of owning count?

A18: The value the car loses, fuel or charging, insurance, service (with tyres and repairs) and loan interest, added up month by month over the years you keep it and the distance you drive. You see the cost a month, a km and in all, and which part is the biggest.

Q19: Why does AutoCalc ask me for the value a car loses?

A19: How fast a car loses value depends on the model, its condition, the km and the city, and no published figures fit every car, so AutoCalc does not guess. Type the resale price you expect when you sell it, or the share it loses in its first year and in each year after; used-car listings for your model are the best guide. Until you do, the page says the value lost is not counted and the cost is too low.

Q20: How does it work out when a dearer car pays for itself?

A20: For each pair of cars, it adds up how much less the dearer one costs to run (fuel, insurance, service and interest) month by month, and finds when that reaches the difference in price. If it never does in the years you keep the car, it says how many years it would take. The totals, unlike this payback, also count what each car is worth when you sell it.

Q21: Do fuel prices rise in the calculation?

A21: Only if you say so: type a yearly rise under Fuel prices rise, and each year's fuel costs that much more than the year before. Left empty, prices stay as you typed them.

Q22: What is the IDV, and how is it worked out?

A22: The insured declared value is the most the insurer pays if the car is stolen or written off. It is the maker's listed price less a share for age from the India Motor Tariff: 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 ex-showroom price when new and the age under What a car is worth.

Q23: Can I compare owning a car with taking cabs?

A23: Yes. Type the cab fare a km (or a mile) and AutoCalc compares what the same distance would cost by cab with owning the car, before counting waiting times and trips you would not take.

5. Trips and Charging

Q24: How is a trip's cost worked out?

A24: The distance (doubled for a round trip) divided by your real mileage gives the fuel or electricity, times its price; tolls (both ways if you choose) and parking or other shared costs are added, and the total is split between the people sharing. Share the split copies it to send.

Q25: How are the fuel or charging stops counted?

A25: Type the tank size, or for an electric car the usable battery and the charge at the start. A refill is counted when about 10% is left, filling 90% of the tank; an electric car is counted as charging from 10 to 80%.

Q26: Where do the CO2 figures come from?

A26: From burning the fuel: petrol 2.35 kg a litre and diesel 2.69 kg, from the US EPA's figures for a gallon (8,887 g and 10,180 g); CNG 2.75 kg a kg, counted as methane. For electricity, India's grid average for 2025-26, 0.675 kg a kWh, from the Central Electricity Authority's CO2 Baseline Database.

Q27: How long does charging take?

A27: Under Charging, type the usable battery, the charge now and the charge you want, and choose the charger. Home (AC) charging runs at the lower of the charger's and the car's power until nearly full; fast (DC) charging slows after about half full and crawls above 80%. The table compares the same charge on every kind of charger. The times are estimates from typical charging curves; curves differ between cars.

Q28: What is charging efficiency?

A28: The share of the electricity from the grid that reaches the battery; the rest is lost as heat. Leave the box empty and AutoCalc assumes 88% on AC and 93% on DC, or type your own figure. The cost is worked out on the electricity from the grid.

Q29: How do I find my real mileage without the garage?

A29: Under Mileage, fill the tank to full, drive, fill to full again, and type the distance and what the second fill took. AutoCalc shows the mileage in every unit, and Convert turns any mileage into the others.

6. Tyres

Q30: How do I read a tyre size such as 205/55 R16 91V?

A30: 205 is the width in mm, 55 the sidewall height as a percent of the width, R means radial, 16 is the rim size in inches, 91 is the load index (615 kg for each tyre) and V the speed rating (240 km/h). Under Read a sidewall, type the marks on your tyre and each part is explained, with XL (extra load), RF (run-flat), C (a commercial tyre) and the P and LT marks of American sizes.

Q31: Can I fit a different tyre size?

A31: Compare the size now on the car with the new one. A common guide is to keep the overall diameter within about 3% of the original, so the speedometer, ABS and clearance stay close to what the car was built for; 3 to 5% needs care, and more than 5% is not advised. Keep the load index and speed rating at least as high as the owner's manual asks.

Q32: What does the speedometer show with a different size?

A32: A taller tyre turns fewer times for each km, so the speedometer and the odometer read less than you really do; a smaller one makes them read more. The table shows the real speed for each reading from 20 to 140.

Q33: How old is my tyre, and when should I replace it?

A33: The last four digits of the DOT code are the week and year it was made: 2423 is week 24 of 2023. Rubber ages even unused: Michelin advises a check every year from 5 years old, and tyre makers such as Michelin and Continental advise replacing tyres 10 years after they were made at the latest; some car makers say 6.

Q34: How much tread is enough?

A34: 1.6 mm is the legal minimum in many countries and where the wear bars in the grooves sit. Continental advises replacing at 3 mm, because below it stopping on a wet road takes much longer; in India, before the monsoon is a good time to check.

7. Power and Performance

Q35: How accurate is the 0 to 100 km/h figure?

A35: It is a rough estimate from a simple model of the car accelerating with the grip of its driven wheels, the power that reaches them, gear changes, air drag and rolling resistance. Weight, tyres, launch control, heat and altitude change real times, and the maker's figure is the one to trust. It is useful to compare cars, or to see what extra people on board do.

Q36: How are power, torque and rpm related?

A36: Power in kW is torque in Nm times rpm divided by 9,549. Type two of the three and AutoCalc works out the third, in PS (735.5 W), bhp and hp (745.7 W), kW and watts, and torque in Nm, lb-ft and kgm.

Q37: How are the speeds in each gear worked out?

A37: Road speed is the engine speed times the tyre's circumference divided by the gear ratio times the final drive. Type the gear ratios, first gear first, the final drive and the redline; the tyre size comes from the Tyres tab unless you type one. The table shows the speed for each 1,000 rpm, at the redline, the rpm at 100 km/h, and where the rpm drops after each change.

8. Your Garage

Q38: How does the garage work out my real mileage?

A38: Fill the tank to full and tick Full tank. The real mileage is the distance from one full tank to the next divided by all the fuel put in between, so a part fill is counted at the next full one. You see the average, the last and the best, and a chart of each full tank.

Q39: What if I forget to log a fill-up?

A39: Tick "I missed logging the last fill-up" on the next one. The stretch before it is left out instead of spoiling the figure, and counting starts again from that fill-up if it is a full tank.

Q40: How do the service reminders work?

A40: Each reminder is due by distance, by time, or both, whichever comes first, counted from when it was last done. The date for the distance is worked out from how far you drive a day, from your log. A reminder shows Due soon in its last stretch and Overdue after. Press Done to log the service; ticked reminders start counting again from that date and odometer.

Q41: Where do the service intervals come from?

A41: A new vehicle starts with example intervals for its fuel (for a petrol car, the periodic service every 10,000 km or 12 months, the air filter every 20,000 km or 24 months, and so on). They are examples, not your car's: change each one to your owner's manual, delete the ones that do not apply and add your own.

Q42: How long do papers like the PUC and the registration last?

A42: 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. Type the date each paper runs out; it warns 30 days before, and Renewed moves the date on by the months you set.

Q43: Can I add the due dates to my phone's calendar?

A43: Yes. Add the due dates to a calendar saves a calendar file with every reminder and paper that has a date, each with an alert three days before. Open it on your phone or computer to add them.

Q44: Can I export or import my log?

A44: Spreadsheet saves the log as a CSV file. Import reads a CSV file with at least a Date column and an Odometer or Total column (Type, Quantity, Full, Missed, Category and Note are used when present; miles and gallons are read from the column names), skips entries already in the log, and can be undone. Files over 5 MB are refused.

9. Your Data

Q45: Where is my data kept?

A45: In this browser's storage on this device, so it is there next time. Nothing is written until you type or choose something, and a private window or cleared browser data starts empty.

Q46: How do I move it to another device or keep a copy?

A46: Settings, Your data: Save a backup writes everything to a file; Open a backup on the other device replaces what is there with it, after you confirm. Files over 10 MB are refused, and every value in a backup is checked before it is used.

Q47: How do I delete everything?

A47: Settings, Your data, Delete everything, after you confirm. It removes AutoCalc's data from this browser and leaves the rest of the site alone. To remove one vehicle, open it with Edit and press Delete vehicle.

Q48: I used AutoCalc before. Is my data still there?

A48: The garage and the tools saved by the earlier AutoCalc in this same browser are brought over the first time the page opens. Its own light and dark setting is not: the site's sun and moon button sets the theme.

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