How does the petrol vs diesel calculator compare costs?

It divides the same distance by each vehicle's entered km/L efficiency, multiplies the resulting litres by the matching fuel price, and compares those fuel costs for the selected period.

Does diesel always cost less to run?

No. The result depends on real fuel efficiency, local petrol and diesel prices, and distance travelled. Diesel may use fewer litres yet still cost more when its price or efficiency difference makes the total higher.

What mileage figures should I enter?

Use real km/L measured under comparable routes, loads, traffic, and driving conditions. Comparing an advertised highway figure with a city-driving figure would produce a misleading result.

How is the diesel break-even point calculated?

When both vehicle prices are entered, the calculator divides the positive diesel purchase-price premium by annualized diesel fuel savings. It shows no break-even when diesel is not dearer to buy or does not save fuel cost.

Does the comparison include maintenance and resale value?

No. It compares fuel expense and an optional purchase-price difference only. Servicing, repairs, taxes, insurance, financing, emissions equipment, depreciation, and resale value are excluded.

Can I compare two different vehicles?

Yes, if you enter the real efficiency and purchase price for each specific vehicle. For a fair comparison, use the same distance period and similar operating conditions.

Can I use any currency?

Yes. Enter both fuel and vehicle prices in the same currency and type its code as the result label. The calculator does not fetch prices or convert exchange rates.

Fuel comparison

Petrol vs Diesel Calculator

Compare petrol and diesel fuel consumption, cost per period, annualized difference, and an optional purchase-price break-even. Every price and efficiency assumption comes from you.

Bike, scooter, car, or truck
Privacy-first
Annual forecast included

Compare petrol and diesel running cost

Metric inputs · fuel-only comparison · optional purchase-price break-even

Distance travelledKilometres in the selected periodDistance periodPetrol efficiency (km/L)Diesel efficiency (km/L)Petrol price per litreDiesel price per litreCurrency code

Petrol vehicle price (optional)Diesel vehicle price (optional)

Petrol

Fuel required

83.33 L

Fuel cost

PKR 23,333.33

Diesel

Fuel required

62.5 L

Fuel cost

PKR 18,125

Fuel-cost difference per month

PKR 5,208.33 less with diesel

Annualized difference: PKR 62,500

Check formulas and limitations

Instructions

How to Compare Petrol and Diesel Running Costs

Enter the distance driven in a day, week, month, or year.
Enter each vehicle's real fuel efficiency in kilometres per litre.
Enter local petrol and diesel prices per litre in the same currency.
Optionally enter both purchase prices to estimate when diesel fuel savings recover a higher diesel price.
Compare litres used, fuel cost, the difference, and the annualized result.

Use equivalent vehicles and operating conditions. This tool answers a fuel-cost question; it does not decide which engine, model, or powertrain is best for every owner.

Exact math

Petrol vs Diesel Cost Formulas

Petrol litres = distance ÷ petrol km/L

Diesel litres = distance ÷ diesel km/L

Fuel cost = litres × price per litre

Difference = petrol cost − diesel cost

Annual savings = period savings × periods/year

Break-even years = diesel price premium ÷ annual diesel fuel savings

Annual multipliers are 365 for daily distance, 52 for weekly distance, 12 for monthly distance, and 1 for annual distance. Full precision is retained during calculation; displayed values are rounded.

Worked example

Monthly Petrol and Diesel Comparison

Inputs: 1,000 km/month; petrol vehicle 12 km/L; diesel vehicle 16 km/L; petrol PKR 280/L; diesel PKR 290/L.

Petrol: 1,000 ÷ 12 = 83.333 L; 83.333 × 280 = PKR 23,333.33

Diesel: 1,000 ÷ 16 = 62.5 L; 62.5 × 290 = PKR 18,125

Monthly diesel fuel saving = PKR 5,208.33

Annualized fuel saving = 5,208.33 × 12 = PKR 62,500

If the diesel vehicle costs PKR 500,000 more, the fuel-only break-even is 500,000 ÷ 62,500 = 8 years. Maintenance, finance, tax, insurance, and resale could change the ownership outcome.

Comparison inputs

Mileage, Fuel Price, Distance, and Driving Conditions

Real-world fuel efficiency

Engine size, vehicle mass, transmission, payload, towing, tyre pressure, traffic, idling, gradients, speed, air conditioning, trip length, and driving style can change consumption. Use measured petrol and diesel mileage from comparable use rather than mixing unrelated test conditions.

Local fuel price

Petrol and diesel prices can move independently. Enter current prices from the same market and update the comparison when prices change. Currency is a label only; no live fuel-price feed or exchange conversion is used.

Distance and period

Annualizing a representative month can support budgeting, but seasonal mileage may differ. Enter annual distance directly when work patterns, holidays, weather, or long journeys make a typical month unreliable.

Decision context

When a Fuel-Savings Break-Even Is Meaningful

A break-even estimate needs a positive diesel purchase-price premium and positive annual diesel fuel savings. If either purchase price is missing, the calculator deliberately omits break-even. If diesel costs less to buy, or petrol has the lower fuel bill, dividing a premium by savings would not describe a valid diesel payback period.

Even a valid fuel-only break-even is not total cost of ownership. Compare user-supplied servicing, repairs, financing, registration, tax, insurance, depreciation, resale value, and any emissions-system costs separately before making a purchase decision.

Scope

Limitations, Entities, and Search Intent

This page covers petrol, gasoline, diesel, fuel efficiency, km/L, litres, distance, pump price, running cost, annual fuel expense, purchase-price premium, savings, and payback period. Petrol and gasoline are treated as the same fuel label; diesel remains a separate input.

It does not estimate CNG or electric charging, fleet dispatch, commercial profitability, maintenance schedules, emissions, or vehicle resale. For a single petrol journey use the trip petrol calculator; for ordinary petrol spending use the general petrol calculator. This boundary avoids duplicating the intent of those tools.

FAQ

Petrol vs Diesel FAQs

Answers about efficiency, fuel prices, running cost, and break-even assumptions.

Transparent calculation

Methodology and Accuracy

The calculator uses the visible metric formulas without external data. Results depend entirely on the entered distance, km/L values, prices, period, currency, and optional vehicle prices. Inputs must be positive; zero and negative values are rejected.

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

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