Vehicle Mileage Calculator
Measure real-world fuel efficiency between fill-ups. Enter distance travelled and fuel used to see km/L, L/100 km, US MPG, and Imperial MPG without entering a fuel price.
Kilometres per litre
12.50 km/L
Litres per 100 km
8.00 L/100 km
US miles per gallon
29.40 US MPG
Imperial miles per gallon
35.31 Imp MPG
Full-tank method
How to Measure Actual Vehicle Mileage
- Fill the tank to a repeatable level and note the odometer, or reset the trip meter.
- Drive normally through a representative mix of routes.
- Refill at the same level, ideally at the same pump orientation.
- Record litres or gallons added; this approximates fuel consumed.
- Subtract the first odometer reading from the second, or read the trip meter.
- Enter distance and fuel with their exact units.
One tank can be affected by pump shutoff and refill angle. Record several fill-ups and divide their combined distance by combined fuel for a more stable real-world average.
Formulas
Mileage and Fuel-Consumption Formulas
km/L = kilometres travelled ÷ litres used
L/100 km = litres used ÷ kilometres × 100
US MPG = miles travelled ÷ US gallons used
Imperial MPG = miles travelled ÷ Imperial gallons used
Conversions use 1 mile = 1.609344 kilometres, 1 US gallon = 3.785411784 litres, and 1 Imperial gallon = 4.54609 litres. Calculations keep full precision internally and round displayed results to two decimals.
Worked example
Mileage Calculation from Two Fill-Ups
A driver fills the tank, resets the trip meter, travels 500 km, then adds 40 litres to refill it.
km/L = 500 ÷ 40 = 12.50 km/L
L/100 km = 40 ÷ 500 × 100 = 8.00 L/100 km
US MPG = 29.40 US MPG
Imperial MPG = 35.31 Imperial MPG
The MPG values differ because US and Imperial gallons have different volumes. This example measures fuel efficiency only; petrol price and journey cost are not part of the calculation.
Reading results
km/L, L/100 km, US MPG, and Imperial MPG
Distance per fuel unit
km/L and MPG tell you how far the vehicle travels per unit of fuel. A higher value means greater efficiency. Always state whether MPG is US or Imperial.
Fuel per fixed distance
L/100 km tells you how much fuel is consumed over 100 kilometres. A lower value means greater efficiency. Convert between metric measures using L/100 km = 100 ÷ km/L.
Use the result in cost calculators
Once you have an observed average, enter it in the trip petrol calculator, daily calculator, or monthly calculator with your local petrol price.
Accuracy
What Can Change a Mileage Measurement?
Refill consistency
Automatic pump shutoff, vehicle angle, temperature, and topping off can change the recorded fuel amount.
Route and traffic
Short trips, congestion, idling, gradients, wind, and road surface affect fuel consumption.
Vehicle and load
Tyre pressure, maintenance, cargo, passengers, roof racks, towing, and air conditioning can alter efficiency.
Driving behaviour
Speed, acceleration, braking, gear selection, and warm-up habits can make tank-to-tank results vary.
Compare like with like. A city-only tank should not be treated as an exact prediction for steady highway travel. An average across several representative tanks is usually more useful than one unusually good or poor result.
Scope
Limitations and Assumptions
The calculator assumes the entered distance and fuel volume are positive, accurate, and refer to the same measurement period. It assumes the second full refill replaces the fuel consumed after the first full refill.
Odometer error, tyre-size changes, fuel leaks, pump calibration, incomplete fills, fuel used while stationary, and mixed operating conditions can affect the measurement. The result is an estimate of observed efficiency, not a manufacturer rating, mechanical diagnosis, emissions figure, or total ownership cost.
This page targets actual mileage and fuel-consumption measurement. It does not attempt to rank for petrol expense, trip cost, fuel-price comparison, or monthly budgeting queries served by dedicated cost calculators.
FAQ
Vehicle Mileage Questions
Answers about full-tank measurement, metric consumption, gallon types, and real-world variation.
Transparent calculation
Methodology and Review
The calculator normalizes entries to kilometres and litres, derives all four measures from the same unrounded quantities, and rounds only the displayed results. No account, location, fuel-price feed, or exchange rate is required.
See the sitewide calculation methodology and petrol expense formula guide. Last reviewed: 3 August 2026.
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