How to convert 21 mpg to L/100 km
Liters per 100 km is the inverse of miles per gallon, so you divide a constant by the mpg value:
L/100 km = 235.215 ÷ 21 = 11.20
The constant 235.215 comes from 100 km ÷ 1.609344 km per mile × 3.785411 liters per US gallon.
What 21 mpg means in practice
| Fuel per 100 miles | 4.76 gallons |
| Fuel per 100 km | 11.20 liters |
| Fuel for 12,000 miles a year | 571 gallons |
| Fuel cost for 12,000 miles at $3.20/gal | $1,829 |
| CO₂ per mile (gasoline) | 423 g |
CO₂ is based on the EPA figure of 8,887 grams of CO₂ per gallon of gasoline. For your own trip costs, use the fuel cost calculator.
Is 21 mpg good?
This is average fuel economy for many SUVs, crossovers and larger sedans.
Values around 21 mpg
| US mpg | L/100 km | UK mpg | km/L |
|---|---|---|---|
| 17 mpg | 13.84 L/100 km | 20.4 UK mpg | 7.23 km/L |
| 18 mpg | 13.07 L/100 km | 21.6 UK mpg | 7.65 km/L |
| 19 mpg | 12.38 L/100 km | 22.8 UK mpg | 8.08 km/L |
| 20 mpg | 11.76 L/100 km | 24.0 UK mpg | 8.50 km/L |
| 21 mpg | 11.20 L/100 km | 25.2 UK mpg | 8.93 km/L |
| 22 mpg | 10.69 L/100 km | 26.4 UK mpg | 9.35 km/L |
| 23 mpg | 10.23 L/100 km | 27.6 UK mpg | 9.78 km/L |
| 24 mpg | 9.80 L/100 km | 28.8 UK mpg | 10.20 km/L |
| 25 mpg | 9.41 L/100 km | 30.0 UK mpg | 10.63 km/L |
Frequently asked questions
What is 21 mpg in L/100 km?
21 US mpg equals 11.20 L/100 km (235.215 ÷ 21).
What is 21 mpg in km/L?
21 US mpg equals 8.93 kilometers per liter.
Is 21 mpg good?
This is average fuel economy for many SUVs, crossovers and larger sedans.
What is 21 US mpg in UK mpg?
21 US mpg equals 25.2 imperial (UK) mpg.
Last updated November 10, 2026