Estimate distance using either kilometers per liter or liters per 100 kilometers, recognize their reciprocal relationship, and keep usable fuel and real-world variation visible.
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The calculation
Distance (km) = liters × km/L = liters ÷ (L/100 km) × 100
Worked example
20 L at an assumed 12.5 km/L gives 250 km. The equivalent consumption is 8 L/100 km, so 20 ÷ 8 × 100 also gives 250 km. Reserving 2 L leaves 18 L for the model and an estimated 225 km.
Economy is assumed constant in the calculation. Traffic, terrain, weather and other conditions change actual use; a theoretical range is not a guarantee or advice to run a tank empty.
Video chapters
- 0:00 — Liters alone cannot tell you the distance
- 0:16 — Kilometers per liter tells us what to multiply
- 0:34 — Check by dividing distance by economy
- 0:50 — Liters per 100 kilometers reverses the rate
- 1:05 — The two ratings are reciprocals with a factor
- 1:22 — Use fuel allocated to the estimate
- 1:43 — A fixed-rate estimate is not a guarantee
- 2:02 — Read the rate, then calculate
Read the full transcript
How far can twenty liters of fuel take a vehicle? We also need its fuel economy. The same fuel volume can produce different distances in different vehicles or conditions. We will use a hypothetical constant rate to show the calculation, then separate that model from real driving range.
Suppose the vehicle averages twelve point five kilometers per liter. Each liter corresponds to twelve point five kilometers in this model. Multiply twenty liters by twelve point five kilometers per liter. Liters cancel, leaving two hundred fifty kilometers. The fuel portions and road segments build the same total together.
Divide two hundred fifty kilometers by twelve point five kilometers per liter. That returns twenty liters. This reverse check is useful because it reveals a misplaced multiply or divide. The equation links three quantities: fuel volume, distance per unit fuel, and total modeled distance.
Another common rating is liters per one hundred kilometers. Suppose it is eight. That means eight liters are used for each hundred-kilometer block. Divide twenty liters by eight liters per block to get two point five blocks. Multiply by one hundred kilometers: the same two hundred fifty kilometers.
Eight liters per hundred kilometers corresponds to one hundred divided by eight, or twelve point five kilometers per liter. A lower liters-per-hundred-kilometers number means less fuel used for the same distance. A higher kilometers-per-liter number means more distance from the same fuel. Read the unit before choosing the operation.
If you choose to hold two liters out of the calculation as a hypothetical reserve, only eighteen of the twenty liters are allocated to the modeled trip. Eighteen times twelve point five gives two hundred twenty-five kilometers. That reserve is an example assumption, not a universal recommendation for any vehicle.
Actual consumption changes with driving conditions. Traffic, speed, terrain, temperature, and vehicle load can affect the result. A published or previous average may not match the next trip. Do not treat a calculated maximum as a promise that all fuel is usable or that the vehicle will reach that distance.
With kilometers per liter, multiply fuel by economy. With liters per hundred kilometers, divide fuel by consumption and multiply by one hundred. State the available fuel and the assumed rate. Twenty liters at twelve point five kilometers per liter gives a modeled two hundred fifty kilometers.
Sources
- Natural Resources Canada — fuel consumption tables
- Natural Resources Canada — understanding fuel consumption ratings