I've played time controls ranging from hyperbullet to OTB tournament games lasting longer than 5 hours. During these times there are many things related to my calculation that I wished I could do better such as visualizing more clearly or choosing candidate moves more efficiently. But never once did I wish I could calculate faster.
So it's a strange question to me. I think maybe you're either unusually slow at calculation, or maybe you mean something else... for example maybe you wish you could verify a move is safe more quickly or something.
How do i improve my calculation speed? Does it come with more consistent puzzle practise or shall i start playing lots and lots of blitz games. Iv heard the latter is a little counter-productive from many experienced chess players