Fuel Efficiency Comparison Calculator
Compare two cars or bikes by mileage, fuel type, energy price, monthly distance, and maintenance to see which one costs less to run.
Compare two vehicles
Use km/l for petrol or diesel and km/kWh for EV.
Vehicle A
Vehicle B
| Metric | Vehicle A | Vehicle B |
|---|---|---|
| Vehicle price | -- | -- |
| Cost per km | -- | -- |
| Monthly fuel/energy cost | -- | -- |
| Monthly cost with maintenance | -- | -- |
| Yearly cost with maintenance | -- | -- |
What is fuel efficiency comparison?
Fuel efficiency comparison helps you understand how much two vehicles cost to run for the same monthly distance. A higher mileage vehicle usually costs less, but fuel price, EV electricity price, and monthly maintenance can change the final result.
Use this calculator for cars, bikes, scooters, EVs, diesel vehicles, or petrol vehicles. For EVs, enter efficiency as km per kWh and electricity price as rupees per unit.
How Running Cost Is Actually Calculated
The core formula behind every number on this page is simple: cost per km equals fuel or electricity price divided by efficiency. From there, monthly fuel cost is cost-per-km multiplied by your monthly distance, and total monthly cost adds your maintenance estimate on top. Yearly cost is just the monthly total multiplied by 12 — that yearly figure is what the calculator actually uses to decide which vehicle is cheaper, not the cost-per-km number alone, because maintenance cost doesn't scale with distance the way fuel cost does.
A Worked Example: Petrol Car vs. EV Hatchback
Using the calculator's own sample values — a petrol car at 16 km/l with fuel at Rs. 105/L and Rs. 1,500/month maintenance, against an EV hatchback at 7 km/kWh with electricity at Rs. 8/unit and Rs. 700/month maintenance, both driven 1,200 km a month — the petrol car costs about Rs. 6.56 per km to run, while the EV costs about Rs. 1.14 per km. That gap compounds fast: petrol's monthly total (fuel plus maintenance) comes to roughly Rs. 9,375, versus about Rs. 2,071 for the EV — a yearly saving of close to Rs. 87,600 in running costs. But the EV in this example costs Rs. 3,00,000 more upfront (Rs. 13,00,000 vs. Rs. 10,00,000). Dividing that upfront gap by the monthly saving shows the extra cost pays for itself in about 41 months, or roughly 3.4 years — after that point, the EV is cheaper overall even accounting for its higher purchase price.
Common Mistakes When Comparing Vehicles
The most common one is comparing running cost alone and ignoring the upfront price gap — a vehicle with a lower cost per km isn't automatically the better financial choice if it costs significantly more to buy and you won't keep it long enough to recover that difference through running savings. Another is using an unrealistic monthly distance; cost-per-km is the same regardless of distance, but the rupee amount of savings only becomes meaningful at the distance you'll actually drive, so entering your real average monthly kilometers (not a rounded guess) matters for the payback-period estimate. People also sometimes enter ARAI-certified mileage figures without adjusting for real-world driving, which for petrol and diesel vehicles typically runs lower in city traffic than in standardized test conditions — using a realistic, slightly lower mileage figure than the brochure number gives a more honest cost estimate. Finally, EV efficiency (km/kWh) and electricity price can vary a lot depending on whether you mostly charge at home on a domestic tariff or at public fast chargers, which are usually priced higher per unit — use whichever charging pattern actually reflects your real usage.
Comparing Petrol, Diesel, and EV Fairly
Because this calculator uses cost-per-km as its common unit, you can directly compare vehicles running on completely different energy types — petrol, diesel, or electricity — without needing to convert between them yourself. The trade-off to keep in mind is that diesel vehicles typically carry a higher purchase price and higher maintenance cost than an equivalent petrol variant, but usually offer better mileage and a lower per-litre fuel price, so diesel tends to make more financial sense only at higher monthly distances — entering a low monthly distance can make a diesel vehicle look like the worse choice even though it would win out for a high-mileage driver. EVs remove fuel-price volatility from the equation almost entirely, since electricity tariffs move far less than petrol and diesel pump prices, which is worth factoring in separately from the raw cost-per-km number if you're trying to budget several years ahead.