Do you mean the head required to supply the house system? If this is what you are asking then maybe it be be something like the vertical height from the pump to the highest point in the house plus the friction loss in the pipework . Time for you to do some reading and research. How about starting with Google - how to -----
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
If you know the RPM and Impeller diameter, shutoff head can be estimated.
Typical common pump discharge head at operating conditions would be roughly about 80% of Shutoff head.
A low grade pump found around the house built for low heads and designed for use where efficiency was not a concern could be as low as 50% of shutoff head.
Are you trying to calculate a requirement or find out capacity of an existing pump?
Existing pump needs manufacturer and model no and then you can find most pump data on the vendors website, even small domestic pumps. You could test it yourself, but that seems a bit extreme...
New pump head will vary depending if this is a once through end point delivery (a tap or tank) when you need to add static head to friction losses or a circualtion mode (radiators or HXs) when it is friction losses in the pipes and equipment only which is pressurised.
Posts above give you some good guidance, but your post is a bit vague so gets a vague response I'm afraid....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
