What it does
CNG costs less per kilometre than petrol, but a CNG variant or a fitted kit costs extra up front. This tool shows the cost per kilometre of each fuel, how much you save in a month, and how many months it takes for the saving to cover the extra cost.
Use your own real mileage for both fuels, which you can measure with real mileage. To work out a whole year of petrol, use fuel cost, and to compare with an electric car try EV vs petrol.
How to use it
- Type the kilometres you drive in a month.
- Type the petrol price per litre and your petrol mileage in km/L.
- Type the CNG price per kg and your CNG mileage in km/kg.
- Type the extra cost of the CNG variant or kit, and how many years you will keep the car.
- Read the cost per kilometre, the monthly saving and the payback.
What each setting does
- Gas: CNG (price per kg, km per kg) or LPG (price per litre, km per litre).
- Extra cost: the factory CNG premium or the kit and fitting.
- Years kept: shows what you save in total over that time, after paying the extra cost.
Worked example
1,500 km a month. Petrol at ₹105 per litre and 15 km/L costs ₹7.00 per km. CNG at ₹90 per kg and 22 km/kg costs ₹4.09 per km. You save ₹2.91 per km, about ₹4,364 a month. With ₹95,000 extra, payback is about 21.8 months.
FAQs
What else should I think about? Boot space (the cylinder takes room), queues at CNG stations, and fewer stations on some routes.
Can I fit a kit myself? No. Fit only a government-approved kit, from an approved fitter, and have the change endorsed on the RC (registration certificate). Rules as checked November 2026; check the official source.
Is the saving guaranteed? No. It depends on future prices and your real mileage.
Where the numbers come from
- Simple arithmetic on the prices and mileages you type: cost per km = price / mileage; payback = extra cost / monthly saving. Prices change often, so use today's pump prices. Fitting rules as checked November 2026; check the official source (the transport department and the vehicle maker). Drawings are fibub's own.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-12.