I m not sure what exactly you are trying to calculate. Can you give a bit more detail?
lets take India vs Sri lanka as an example
currently there are 0.1375 BTC in the pool
odds are : India 1.07 Sri Lanka 6.55 Tie : 34.31
let's say I want to bet 0.02 BTC on Tie , such calculator can do the math and tell me how my bet will affect the odds so it will tell me if I place the bet how it will change the odds for all of the selections
and since onehash had one I guess freebitcoin can have one as well
On the tie, you will get 34.31. It means you will get 0.02 x 34.31 = X amount of btc.