MPG to L/100km Converter
Turn a miles-per-gallon figure into litres per 100 km after you say whether that MPG used a US liquid gallon or an Imperial gallon. Thirty US MPG is about 7.84 L/100 km; the same “30” as Imperial MPG is about 9.42 — a thirstier metric number because the gallon was larger.
Updated
How to use
- Enter the MPG from the sticker, handbook or trip computer.
- Select the gallon that figure was measured with. US for EPA and US pumps; Imperial for older UK mpg.
- Read L/100 km to two decimals. Zero MPG is rejected (infinite consumption is not shown).
- Paste that L/100 km into Fuel Cost or Road Trip Cost if you want litres and money for a kilometre trip.
How it works
This is the inverse of L/100 km → MPG, with the same constants: 1.609344 km per mile, 3.785411784 L per US gallon, 4.54609 L per Imperial gallon. Higher MPG becomes lower L/100 km for a given gallon. The lookup table on this page is US MPG only — 20, 25, 30, 35, 40 US MPG map to 11.76, 9.41, 7.84, 6.72, 5.88 L/100 km. Imperial 30 mpg is not on that table because it is a different input.
The dangerous mix-up is treating a US window sticker as Imperial. You would report about 9.42 L/100 km instead of 7.84 and the car would look needlessly greedy. The opposite mix-up makes a UK figure look more efficient than it is. If you are unsure, convert both and compare to a European handbook line that already prints L/100 km.
Zero MPG is undefined — it would be infinite litres per 100 km — and is rejected. Negative MPG is rejected. The converter does not know WLTP versus EPA versus a sloppy tank fill. It converts the number, not the test cycle.
Once you have L/100 km, trip fuel is (km ÷ 100) × that number. Road Trip Cost and Fuel Cost take it from there. This page will not add tolls or a pump price.
Canada and some other markets print L/100 km on the window and MPG as a courtesy. Use the metric number when you have it; converting MPG back and forth only adds rounding.
Formula
L/100 km = (100 × litres per gallon) ÷ (MPG × 1.609344 km/mile)
Worked examples
30 US MPG
30 US MPG → 7.84 L/100 km
30 Imperial MPG
30 Imperial MPG → 9.42 L/100 km
US MPG to L/100 km
| US MPG | L/100 km |
|---|---|
| 20 | 11.76 |
| 25 | 9.41 |
| 30 | 7.84 |
| 35 | 6.72 |
| 40 | 5.88 |
Useful notes
- Select the gallon that the MPG figure was measured with.
- Zero MPG is undefined (infinite consumption) and is rejected.
- The on-page table is US MPG. Imperial 30 mpg is 9.42 L/100 km, not 7.84.
FAQ
- My car says 30 mpg. Which gallon is that?
In the United States it is almost always the US liquid gallon. Older UK figures often used the Imperial gallon. If unsure, convert both and compare to the handbook’s L/100 km.
- Does a higher MPG mean lower L/100 km?
Yes, for the same gallon standard. They move in opposite directions.
- Can I use this for trip fuel?
Convert to L/100 km first, then use the Fuel Cost calculator with kilometres.
- Why does the table ignore Imperial MPG?
It is a US-gallon lookup so the columns stay one standard. Convert Imperial MPG in the calculator; 30 Imperial MPG is 9.42 L/100 km.
- Is Canadian “L/100 km” the same identity?
Yes, litres per 100 km is the same unit. If the window already shows it, you do not need this converter.
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