How do you determine what size to make your VARBINARY field to hold the results of the HASHBYTES function?

Is it simply a matter of setting it to be equal to the largest HashByte function input value?

DECLARE @vHashResults AS VARBINARY(40)

DECLARE @vHashInput01 AS CHAR(20)

DECLARE @vHashInput02 AS CHAR(20)

SET @vHashInput01 = 'thisisa20bytechar123'

SET @vHashInput02 = 'thisisa21bytechar1234'

SET @vHashResults = HashBytes('SHA1', @vHashInput01 + @vHashInput02)