How to use Fuel Economy: L/100 km & MPG
Calculate consumption from a measured fill and distinguish US from Imperial MPG.
- Record kilometres travelled and litres used over the same interval.
- Distinguish US from Imperial gallons when reading an MPG figure.
- Compare similar driving conditions rather than treating one tank as a fixed vehicle property.
Formula & calculation method
L/100 km = litres used ÷ kilometres × 100. MPG = miles travelled ÷ gallons used. US gallons are 3.785411784 L; Imperial gallons are 4.54609 L.
Input reference · 2 fields
These labels describe the calculation’s base units. Supported measurements can switch through the header’s region settings; follow the current workspace labels. Prefilled values are examples.
- Distance travelled (km)
- Enter a plain number with a decimal point if needed. The workspace shows an illustrative value, not a recommendation.
- Fuel used (litres)
- For a tank-to-tank estimate, use fuel added to restore the same fill level.
A quick example
Using 45 L over 600 km gives 7.5 L/100 km, approximately 31.3619 US mpg or 37.6641 Imperial mpg.
Assumptions, edge cases & limits
- US and Imperial MPG are different. Tank-to-tank comparisons need a consistent fill level; a single journey may not represent typical driving.
- Distance and fuel must both be positive. Empty fuel or distance values cannot define a meaningful economy figure.
Questions about Fuel Economy: L/100 km & MPG
Why do US MPG and Imperial MPG differ for the same trip?
A US gallon is 3.785411784 litres and an Imperial gallon is 4.54609 litres. The larger Imperial gallon produces a higher MPG figure for the same fuel use.
How do I measure fuel consumption from a fill-up?
Use fuel needed to return the tank to a comparable fill level over a measured distance. Tank-to-tank consistency matters; one fill or driving pattern may not represent long-term average consumption.
Are my files or inputs uploaded?
Calculation and file processing run in your browser without a processing upload. Downloads go to your device. Choosing a next-step transfer creates a temporary local copy for that workflow. Region preferences are stored separately from tool inputs. See our privacy details.
Can I use this tool for free?
Yes. No signup, subscription or payment is required to use the tool or download its output. File tools have device and size limits; a smaller batch may work better on a phone.
Method & references
Read the underlying method or measurement convention in context. These references do not imply affiliation or endorsement.
Natural Resources Canada: consumption units ↗Check the assumptions, measurement conventions and actual product or contract terms for your use case.A result or explanation needs correcting? Tell us the tool name and an example.