How does the petrol vs CNG calculator work?

It divides distance by petrol efficiency in km/L and CNG efficiency in km/kg, then multiplies each fuel amount by its matching local price. It compares total cost and cost per kilometre.

Can I convert litres of petrol directly to kilograms of CNG?

No. A litre is a volume unit and a kilogram is a mass unit. Petrol and CNG also have different energy content and storage conditions, so the calculator keeps each fuel in its own unit.

What CNG mileage should I enter?

Use measured km/kg from the vehicle under representative traffic, load, route, and air-conditioning conditions. Do not reuse a petrol km/L figure as if it were CNG km/kg.

Is CNG always cheaper than petrol?

No. The answer depends on each fuel's real efficiency and local price. Availability, conversion costs, maintenance, tank inspection, and reduced cargo space may also matter but are outside this fuel-only result.

Does this include the cost of a CNG conversion kit?

No. It compares fuel expense only. Installation, certification, inspection, servicing, repairs, finance, depreciation, and resale value are not included.

Can I use any currency?

Yes. Enter both prices in the same currency and use its code as the result label. The calculator does not retrieve live prices or exchange rates.

Why can actual CNG cost differ from the estimate?

Traffic, idling, payload, tyre pressure, engine condition, tuning, driving style, filling pressure, station measurement, and route gradients can change real consumption.

Fuel comparison

Petrol vs CNG Calculator

Compare a petrol vehicle with a compressed natural gas vehicle using the same distance and your real-world efficiency and pump-price inputs. See separate fuel quantities, total expense, and cost per kilometre.

Bike, scooter, car, or truck
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Compare petrol and CNG running cost

Petrol in litres · CNG in kilograms · your local prices

Distance travelled (km)Currency codePetrol efficiency (km/L)Petrol price per litreCNG efficiency (km/kg)CNG price per kilogram

Unit note: litres and kilograms measure different quantities and are not converted into each other. Each fuel is calculated from its own efficiency and price.

Petrol

Fuel required

83.33 L

Fuel cost

PKR 23,333.33

PKR 23.33/km

CNG

Fuel required

55.56 kg

Fuel cost

PKR 12,222.22

PKR 12.22/km

Running-cost difference

PKR 11,111.11 less with CNG

Instructions

How to Compare Petrol and CNG Running Costs

Enter the distance travelled in kilometres.
Enter petrol mileage in km/L and its price per litre.
Enter CNG mileage in km/kg and its price per kilogram.
Use the same currency and comparable driving conditions.
Compare fuel required, total cost, cost per kilometre, and the difference.

Use observed efficiency from the specific petrol and CNG vehicles or operating modes being compared. The tool does not assume that either fuel is cheaper.

Exact math

Petrol vs CNG Cost Formulas

Petrol litres = distance ÷ petrol km/L

Petrol cost = litres × price per litre

CNG kilograms = distance ÷ CNG km/kg

CNG cost = kilograms × price per kg

Cost per km = fuel cost ÷ distance

Difference = petrol cost − CNG cost

Calculations retain full precision and round displayed results. Kilograms and litres remain separate; no direct volume-to-mass conversion is made.

Worked example

Example Petrol and CNG Cost Comparison

Inputs: 1,000 km; petrol 12 km/L at PKR 280/L; CNG 18 km/kg at PKR 220/kg.

Petrol = 1,000 ÷ 12 = 83.33 L; cost = PKR 23,333.33

CNG = 1,000 ÷ 18 = 55.56 kg; cost = PKR 12,222.22

Fuel-cost difference = PKR 11,111.11 less with CNG

This illustrative result depends entirely on the entered efficiency and prices. It is not a universal saving claim.

Real-world inputs

Mileage, Price, Vehicle, and Route Factors

Petrol mileage and CNG mileage

Petrol efficiency is expressed as kilometres per litre, while CNG efficiency is commonly expressed as kilometres per kilogram. Engine tuning, conversion quality, vehicle mass, cylinder load, traffic, gradients, speed, idling, tyre pressure, and air-conditioning use can alter both figures.

Local pump prices

Enter current petrol per-litre and CNG per-kilogram prices from the same market. CNG availability, filling pressure, and station measurements may vary. Currency is a label only, with no exchange-rate conversion.

Comparable conditions

Compare the same distance and similar routes, payloads, seasons, and driving styles. Mixing a petrol highway test with a CNG city average would weaken the comparison.

Scope and safety

Limitations, Assumptions, and Ownership Costs

This calculator covers petrol, gasoline, CNG, compressed natural gas, km/L, km/kg, litres, kilograms, distance, pump price, fuel required, running cost, and cost per kilometre. It excludes conversion-kit purchase and installation, cylinder inspection, certification, maintenance, repairs, insurance, financing, depreciation, resale, emissions, range, refuelling time, and cargo-space effects.

It provides a neutral cost estimate, not installation, maintenance, or fuel-storage advice. Follow the vehicle manufacturer's instructions and applicable rules, and use qualified professionals for CNG system work.

For diesel comparison use the petrol vs diesel calculator. For a single petrol journey use the trip petrol calculator. These boundaries avoid competing with general mileage, trip, and ownership-cost pages.

FAQ

Petrol vs CNG FAQs

Answers about litres, kilograms, mileage, fuel prices, running cost, and limitations.

Transparent calculation

Methodology and Accuracy

The calculator uses only the visible formulas and user-entered distance, efficiency, price, and currency. Positive values are required. It does not fetch vehicle specifications, fuel prices, conversion factors, or exchange rates.

Read the shared calculation methodology and petrol expense formula guide. Last reviewed: 3 August 2026.

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