The cost depends on the size and the weight of the package. Wrap it up securely, address it and take it to the post office. They will weight it and tell you what it will cost to send.
Take it to your local post office and they will help you
Go to a Post Office you moron
How can we know in UK? Ask at own Post Office...
Pointless posting in the UK section you need to ask the NZ Post Office
Start at the post office. They will weigh and measure the package and tell you how much the charge will be.