The Prime Minister says they're still trying to work out how much Prince Harry and Megan Markle's visit will cost the taxpayer.

The Duke and Duchess of Sussex will visit at the end of next month, spending time in Abel Tasman and Rotorua as well as Auckland and Wellington.

Jacinda Ardern says they're still working out the details and costs.

"The rough guise that we've given in the past around royal visits have tended to be around the $1 million mark, but again this is a visit we are still working through."

Ardern says these visits have benefits for New Zealand that we'll be looking to maximise.

"The media contingent that follows the royals is exceptionally large. That's one reason we want to give them good exposure to tourism beauty spots."