Fuel Economy Converter
Convert between L/100 km, km/L, US mpg and UK mpg.
Use the Fuel Economy Converter
Convert between L/100 km, km/L, US mpg and UK mpg.
Calculations happen locally in your browser. ToolLott does not send these inputs to a server for this tool.
How to use it
Enter a value, choose the source and target units, then calculate. Results are rounded for display while calculations use full browser numeric precision.
How the Fuel Economy Converter works
The Fuel Economy Converter expresses the same fuel economy in another supported unit using the exact conversion relationships implemented by ToolLott.
Calculation breakdown
ToolLott will explain the current inputs and displayed result here.
Fuel economy conversion method
Fuel economy mixes reciprocal measures: L/100 km is fuel consumed per distance, while km/L and mpg are distance per fuel. ToolLott therefore converts through reciprocal relationships rather than a simple multiply-by-one-factor rule.
km/L = 100 / (L/100 km)ToolLott uses L/100 km as the reference path for this conversion family.
L/100 km = 100 / (km/L)The target-unit factor converts the normalised quantity into the requested display unit.
| Symbol / input | Meaning | Unit |
|---|---|---|
input | Entered fuel economy value | selected source unit |
source factor | Relationship from source unit to L/100 km | conversion factor |
target factor | Relationship from target unit to L/100 km | conversion factor |
Step-by-step method
- Read the entered fuel economy and selected source/target units.
- Convert the source value to the reference L/100 km using the stored factor or formula.
- Convert the normalised value into the requested target unit.
- Format the result for display while keeping the calculation path reproducible.
Worked example
Nina, a operations coordinator, is comparing a vehicle specification quoted as 10 L/100 km with another listing that uses km/L.
Example inputs
- value = 10
- from = l100
- to = kml
Calculation / processing
For 10 L/100 km: 100 / 10 = 10 km/L.The verified output is 10 km/L.
Lower L/100 km is more efficient, while higher km/L or mpg is more efficient; this reversal is why the conversion is reciprocal.
Assumptions
- US mpg uses the US gallon and UK mpg uses the imperial gallon.
- Fuel economy values must be greater than zero because the reciprocal formula would otherwise be undefined.
Limitations
- Real-world fuel use varies with speed, load, terrain, weather and vehicle condition.
- This converts reported economy figures; it does not predict trip fuel consumption by itself.
Common questions
Why does the Fuel Economy Converter use a base unit internally?
Normalising the source value to one reference unit makes every supported source-to-target combination use one consistent calculation path.
Does conversion change the physical quantity?
No. It expresses the same quantity in a different unit.
Why can the displayed value contain many decimals?
Some unit ratios are not terminating decimals. ToolLott calculates with browser numeric precision and rounds only for display.
Methodology sources
Related ToolLott tools
A realistic way Nina could use this tool
Nina is a operations coordinator.
Nina is comparing a vehicle specification quoted as 10 L/100 km with another listing that uses km/L.
They use the worked values shown in the tool: Value: 10; From: L/100 km; To: km/L.
ToolLott returns “10 L/100 km = 10 km/L”. That gives Nina a concrete figure to check against the real task before they copy it into the next document or decision.
Fictional scenario using realistic example data. For Ready tools, the worked result is tied to the tested example shown in the tool. Replace the figures with your own inputs and independently verify important professional, financial, legal, health or safety decisions.
What this converter is for
Use it to convert between L/100 km, km/L, US mpg and UK mpg.
It sits within ToolLott’s Unit Conversion collection, where you can also convert measurement units for length, area, volume, mass, pressure, flow, power, electrical values and more.