Mileage calculator: find your real km/L or mpg
This mileage calculator — a fuel efficiency calculator for cars, bikes, scooters and autos — works out how far you really travel on a litre, gallon, kilogram of CNG or kWh, using the fill-to-fill method: fill to full and note the odometer, drive, fill to full again and enter what it took. You get km/L, L/100 km and US and UK mpg; CNG km/kg; or EV kWh/100 km, km/kWh, Wh/mi and MPGe — plus your cost per km and per mile.
Keep going and it becomes a fuel log for each vehicle type: add every fill-up, including partial top-ups, to track your average, best and worst on a trend chart, and compare any result with the ARAI, EPA or WLTP figure.
How to use the Mileage Calculator
- Choose Petrol or diesel, CNG (km/kg) or Electric (EV), then kilometres or miles (and litres or gallons for petrol). The example buttons fill in sample readings for a car, bike, CNG vehicle or EV.
- At the next full fill-up, enter the reading at the last full tank, today’s reading and the amount the pump shows.
- Read your mileage in the unit chosen under Show mileage as; every other unit appears underneath.
- Optionally add the price and the claimed mileage.
- To track mileage, add each fill-up to the Fill-up log, unticking Filled to full for a top-up, and press Download CSV to keep a copy.
Mileage Calculator features
Every unit
km/L, L/100 km and US/UK mpg; CNG km/kg, kg/100 km and miles/kg; EV kWh/100 km, km/kWh, Wh/km, Wh/mi, mi/kWh and MPGe.
Separate logs
Petrol or diesel, CNG and EV fill-ups are kept in three separate logs, so a CNG car’s kilograms never mix with litres.
True fill-to-fill log
Partial top-ups are carried into the next full tank, so the figures stay right even when you don’t always fill up.
Average, best, worst and trend
See mileage change with seasons, traffic, tyres or a service.
Claimed vs real
Enter the ARAI, EPA or WLTP figure in any unit and see the percentage you are getting.
Private
The log stays in this browser’s local storage; export it as CSV for your own records.
How the fill-to-fill method works
Fuel gauges and trip computers are estimates. With the fill-to-fill (tank-to-tank) method, the fuel needed to fill up a second time is exactly what the engine used since the first full tank, so mileage is simply distance ÷ fuel added.
Worked example: the odometer read 12,000 km at the last full tank and 12,500 km now, and the pump took 25 litres. 500 ÷ 25 = 20 km/L, which is 100 ÷ 20 = 5 L/100 km, 47.04 mpg (US) and 56.5 mpg (UK). At ₹100 a litre the fuel cost ₹5.00 per km, and the claimed 25 km/L would mean you are getting 80% of it.
If you top up partway between full tanks, log it with Filled to full unticked: its fuel is added to the next full tank. For example, full at 10,000 km, a 10-litre top-up at 10,400 km and 20 litres to fill up at 10,600 km gives 600 km ÷ 30 L = 20 km/L.
- Fill up at the same pump when you can, and stop at the first automatic click — topping off to the brim makes each fill different.
- Use the main odometer, not a trip meter.
- Bikes and scooters have small tanks, so average three or more fills.
- CNG pumps show kilograms; enter that figure, not the price, and fill until the dispenser stops.
Conversions used
The factors come from the exact mile (1.609344 km), US gallon (3.785411784 L) and imperial gallon (4.54609 L). MPGe uses the US EPA’s energy equivalence of 33.705 kWh per gallon of petrol. To convert a single figure between units, use the fuel economy converter.
| From | To | Formula |
|---|---|---|
| km/L | L/100 km | L/100 km = 100 ÷ km/L |
| km/L | mpg (US) | mpg = km/L × 2.352146 |
| km/L | mpg (UK) | mpg = km/L × 2.824809 |
| km/kWh | Wh/mi | Wh/mi = 1,609.344 ÷ km/kWh |
| mi/kWh | MPGe | MPGe = mi/kWh × 33.705 |
Why real mileage is lower than ARAI, EPA or WLTP
Official figures come from standard laboratory cycles — ARAI on the Modified Indian Driving Cycle in India, the EPA cycles in the US and WLTP in the UK and EU. Real driving adds air-conditioning, traffic, speed, short cold trips, luggage and soft tyres, so your figure is usually lower; watch the percentage over several tanks.
For EVs, kWh from a charger or home meter include charging losses, so they read higher than the trip computer. Pick one method and stick to it.
To compare petrol, CNG and electric running costs or plan a trip, use the fuel cost calculator; for distances, the distance calculator; for home charging, the electricity bill calculator.
Mileage Calculator FAQ
How do I calculate my car’s mileage?
Fill the tank to full and note the odometer. Drive normally, then fill to full again and note the litres added. Divide the kilometres driven by those litres: 500 km on 25 L is 20 km/L. The mileage calculator does this and converts it to L/100 km and mpg.
How do I calculate bike mileage?
The same way: fill to full, ride, fill to full again and divide the distance by the fuel added — 240 km on 5 L is 48 km/L. Log at least three fill-ups and use the average.
How do I calculate CNG mileage (CNG average)?
Choose CNG, fill until the dispenser stops, note the odometer, and at the next fill divide the kilometres by the kilograms added: 300 km on 12 kg is 25 km/kg, or 4 kg/100 km.
How do I convert km/L to mpg?
Multiply km/L by 2.352 for US mpg or by 2.825 for UK mpg. So 20 km/L is 47.04 mpg (US) or 56.5 mpg (UK). For L/100 km, divide 100 by the km/L figure.
Why is my mileage lower than the company claims?
Claimed figures come from standard lab tests (ARAI, EPA or WLTP) that leave out your traffic, speed, air-conditioning and load. Getting less is normal; a sudden drop over several tanks is worth a service check.
How do I calculate an electric car’s efficiency?
Divide the kWh charged by the distance and multiply by 100: 45 kWh for 300 km is 15 kWh/100 km = 6.67 km/kWh = 241.4 Wh/mi ≈ 139.6 MPGe.
Where is my fill-up log stored?
Only in this browser’s local storage — never uploaded. Clearing site data deletes it, so download a CSV copy.