Fuel cost per km: what your car or bike really costs to run
Published 9 July 2026 · Bharometer Guides
The short answer
₹/km = fuel price ÷ your real mileage. A car doing 15 km/l on ₹100/l petrol costs ₹6.7 per km; a scooter doing 45 km/l costs about ₹2.2 per km. Multiply by your monthly kilometres and you have your fuel budget — 1,000 km a month in that car is roughly ₹6,700.
Two ways to compute it (they should agree)
From mileage: ₹/km = price per litre ÷ km/l. Use your measured mileage — the full-tank method, not the brochure figure or the dashboard's optimism — or the result inherits the same error.
From spend: ₹/km = total fuel money over a period ÷ kilometres driven in it. This needs no mileage figure at all, just receipts and odometer readings, and it works even if you never fill to full. If the two methods disagree noticeably, your mileage figure is probably flattering you.
A real monthly picture
Take a hatchback averaging 14 km/l on ₹100/l petrol, driven 900 km a month:
- Fuel per km: 100 ÷ 14 = ₹7.1/km
- Monthly fuel: 900 × 7.1 ≈ ₹6,430
- Yearly fuel: ≈ ₹77,000
Numbers like these are why a 1 km/l improvement matters: the same car at 15 km/l saves about ₹5,000 a year. Tyre pressure and timely servicing are usually the cheapest fuel discounts available — your mileage trend (see kitna deti hai) tells you when you've drifted.
Fuel-only ₹/km understates the truth
Fuel is the visible cost; the rest hides in annual lumps. Add service, insurance, PUC, parking, tolls, and repairs, and divide by the same kilometres:
- Fuel: ₹77,000/yr
- Service + consumables: ₹12,000/yr
- Insurance: ₹15,000/yr
- Tolls + parking: ₹8,000/yr
Total ≈ ₹1,12,000 over 10,800 km — a true cost of ₹10.4/km, not ₹7.1. That's the honest number to use when weighing a second car, a CNG conversion (see CNG km/kg), an EV, or just taking cabs.
Getting the inputs right
- Log every fill-up with its odometer reading — spend ÷ distance only works if both sides are complete.
- Use your prices, not city averages. The rate printed on your receipt is the one you actually paid.
- Keep non-fuel costs in the same log so the true ₹/km updates itself instead of living in a year-end spreadsheet.
Your ₹/km, computed live
Bharometer shows cost per km on every fill-up, projects your monthly spend, and (with the Cost Log) folds service, insurance, PUC and tolls into a true running cost — automatically, from the numbers you already log at the pump.
