Most coins have diff1 in format like (~uint256(0) >> 20)
I believe you can determine the hashrate multiplier by subtracting the 20 used in bitshift from the number 32
so it would be 2^12 for this one. or for (~uint256(0) >> 16) it would be 2^(32 - 16)

so really for every algo you simple need the bitshift on a zero value uint256.


hefty1
https://github.com/heavycoin/heavycoin/blob/master/src/main.cpp#L40
00000000ffff0000000000000000000000000000000000000000000000000000
https://github.com/heavycoin/heavycoin-hash-python


keccak
https://github.com/Max-Coin/maxcoin/blob/master/src/main.cpp#L42
https://github.com/wecoin/wecoin/blob/master/src/main.cpp#L44
https://github.com/phusion/node-sha3
https://github.com/GalleonBank/galleon

blake
https://github.com/BlueDragon747/Blakecoin/blob/master/src/main.cpp#L38
https://github.com/BlueDragon747/Blakecoin_Python_POW_Module


bcrypt
https://github.com/TaojingCoin-pd/Taojingcoin/blob/master/src/main.cpp#L35
https://github.com/TaojingCoin-pd/Taojingcoin/blob/master/src/bcrypt.cpp
https://github.com/TaojingCoin-pd/Taojingcoin/blob/master/src/bcrypt.h


scrypt-n
https://github.com/vertcoin/vertcoin/blob/master-0.8/src/main.cpp#L35
https://github.com/scr34m/vertcoin_scrypt
https://github.com/ahmedbodi/stratum-mining/tree/NScrypt


max
https://github.com/Prydie/maxcoin-hash-python
https://github.com/ahmedbodi/stratum-mining-maxcoin


fugue
https://github.com/fuguecoin/fuguecoin/blob/master/src/main.cpp#L40
https://github.com/fuguecoin/fuguecoin


SHAvite-3
https://github.com/inkcoin/inkcoin-project/blob/master/src/main.cpp#L38
https://github.com/inkcoin/inkcoin-project/blob/f729f1070eb6222832f34fbf087b1aea16522962/src/hashblock.h
https://github.com/inkcoin/inkcoin-project
http://www.cs.technion.ac.il/~orrd/SHAvite-3/
https://bitcointalk.org/index.php?topic=481516.0