How much is 20 acre in km?

"Acre" is a unit of area or coverage, as of a bedroom floor, or a plot of land.

"Kilometer" (Km) is a unit of length or distance, as of a finger, a piece of rope, or a trip to the moon.

The two units have different 'dimensions' and are used to measure different quantities.

Neither of them can be converted into the other one.