There is no "hash 160".
hash160 is referred to the result of RIPEMD160 of SHA256 which is the first step used to convert public key to an address:
base58check({version byte}RIPEMD160(SHA256(pubkey)))
Base58check encoding is encoding so it is reversible function. so to get HASH160 simply decode the address (base58 string) then remove the first byte since it is the address version byte then remove the last 4 bytes if the function hasn't already done it since it is the checksum. the remaining 20 bytes will be HASH160.