Mileage Calculator

Fifteen kilometres per litre, or 6.67 litres per hundred

Covering 450 km on 30 litres gives a mileage of 15.00 km/L — which the rest of the world would write as 6.67 L/100km. Both describe the same car. They simply run in opposite directions, and confusing them produces answers that are wrong by a wide margin.

Mileage = distance ÷ fuel consumed Consumption (L/100km) = (fuel ÷ distance) × 100

India, Japan and much of Asia quote km/L, where higher is better. Europe quotes L/100km, where lower is better. The conversion between them is not linear — it is reciprocal:

L/100km = 100 ÷ km/L

so 15 km/L is 100 ÷ 15 = 6.67 L/100km, and 20 km/L is 5.0 L/100km.

Why the reciprocal relationship matters

Because the two scales are inverses, equal steps on one are not equal steps on the other — and this produces a genuinely counter-intuitive result about where efficiency gains are worth chasing.

Improving from 10 to 15 km/L saves 3.33 litres per 100 km. Improving from 20 to 25 km/L — the same five-unit gain — saves only 1.0 litre per 100 km. The first improvement is worth more than three times the second.

The practical implication is that replacing a genuinely inefficient vehicle pays back quickly, while chasing marginal gains on an already-efficient one rarely does. It is also why L/100km is arguably the better scale for decision-making: it is directly proportional to what you actually spend.

Measuring your real figure

Manufacturer figures in India come from the ARAI test cycle, run under controlled laboratory conditions. Real-world results typically land 15–25% below the quoted number, and the gap widens in city traffic.

The tank-to-tank method is the only reliable alternative:

1. Fill the tank completely, to the first click of the nozzle. 2. Reset the trip meter. 3. Drive normally until the tank is low — at least 300 km for a usable sample. 4. Fill completely again, at the same pump if possible, and note the litres added. 5. Mileage = trip distance ÷ litres added.

Repeat over two or three tanks and average. Using the same pump matters because nozzle cut-off points differ, which is the largest source of error in a single measurement.

Reading your result

A single figure conceals considerable variation. Expect roughly:

• City driving — 20–30% below highway figures, from idling, stop-start movement and low gears
• Air conditioning — 5–10% worse
• Full load or roof carrier — 10–20% worse, mostly aerodynamic
• Speeds above 100 km/h — efficiency peaks around 60–80 km/h and falls away sharply
• Tyres under-inflated by 25% — a further 3–5%

The onboard computer is not a substitute for measurement. Instantaneous and average readouts are typically optimistic by 5–10%, because they estimate injector flow rather than measuring fuel actually delivered.

Common mistakes

Comparing km/L against L/100km directly. They run in opposite directions.

Trusting the ARAI figure. It is a test-cycle result, not a prediction.

Measuring over one short tank. Fewer than 300 km gives a sample dominated by the fill-level error.

Filling at different pumps. Cut-off points vary enough to distort a single measurement.

Assuming a five-unit gain is always worth the same. At the efficient end of the scale, it is worth far less.