The formula
Every calculator on this site is a different presentation of the same equation:
Petrol cost = (Distance ÷ Mileage) × Price per unit
The three inputs must agree on units — kilometres with km/L, miles with MPG, or kilometres with L/100 km. The calculator normalizes everything to a common base unit before applying the price; the user just picks the units they think in.
Unit conversions
- 1 mile = 1.609344 km (international agreement, 1959).
- 1 US gallon = 3.785411784 L. 1 UK gallon = 4.54609 L. The two are different — a US MPG figure does not carry over to UK fuel pricing.
- MPG → km/L: multiply US MPG by 0.4251. Equivalently, 25 US MPG ≈ 10.6 km/L.
- L/100 km → km/L: divide 100 by L/100 km. So 8 L/100km = 12.5 km/L.
Default petrol prices
Reference prices below — last updated April 2026. Pump prices change every 1–4 weeks in most countries; the calculator's price field is editable so you can override with today's actual rate.
On first load the calculator detects the user's locale and pre-fills a recent national-average petrol price for the region:
- Pakistan (PKR): ~ ₨ 280 per litre
- India (INR): ~ ₹ 105 per litre
- Bangladesh (BDT): ~ ৳ 130 per litre
- Sri Lanka (LKR): ~ Rs 365 per litre
- UK (GBP): ~ £ 1.45 per litre
- USA (USD): ~ $ 3.40 per US gallon
- Eurozone (EUR): ~ € 1.70 per litre
- Australia (AUD): ~ A$ 1.85 per litre
- Canada (CAD): ~ C$ 1.55 per litre
- UAE (AED): ~ د.إ 3.10 per litre
- Saudi Arabia (SAR): ~ ﷼ 2.33 per litre
- South Africa (ZAR): ~ R 22.50 per litre
Petrol prices change weekly. Confirm today's rate at your local pump or your country's fuel-price authority before relying on the result for a budget commitment.
Default mileage figures
The vehicle selector preloads typical real-world mileage for each segment. These are manufacturer-published midpoints:
- Bike (motorcycle): 35–65 km/L. Default 50 km/L (mid-range 125cc commuter).
- Scooter: 40–55 km/L. Default 50 km/L (Honda Activa class).
- Car: 9–20 km/L. Default 14 km/L (small sedan / hatch).
- Truck / SUV: 7–13 km/L. Default 10 km/L (mid-size SUV / pickup).
Period projections
The result panel projects daily cost across longer windows by simple multiplication — 30 days for the "monthly" figure, 365 days for the "annual". We don't model weekday/weekend split, holidays, or annual leave because those vary too much per user. Override the distance per day to model a working-days-only commute.
Carpool split
The carpool option divides the total trip cost by the number of riders, including the driver. So 4 carpoolers split a ₨ 200 trip into ₨ 50 each. The math doesn't weight by distance traveled per rider — that's a feature for the dedicated carpool-split-calculator on the Phase 2 roadmap.
Where we're less precise
- We use a single mileage figure for the whole trip. Real-world fuel economy varies with stop-and-go traffic, hill grade, AC use, tyre pressure, vehicle age, and driving style — typically ±10% from the manufacturer rating.
- We assume the petrol price is constant across the trip. For out-of-region road trips, refill prices change.
- We don't model losses from vehicle warm-up on short trips, which can knock 5–10% off the calculated mileage on a sub-2 km commute.
Disclaimer
Estimates only. The calculator is a budgeting and planning tool, not a fleet-management or tax-deduction system. Confirm fuel prices with your local pump and verify mileage against your own fill-up records before relying on the output for business expense reporting.