Britain's Queen Elizabeth II poses with her five great-grandchildren and her two youngest grandchildren in the Green Drawing Room, part of Windsor Castle's semi-State apartments. The children are: James, Viscount Severn (left), 8, and Lady Louise (second left), 12, the children of The Earl and Countess of Wessex; Mia Tindall (holding The Queen's handbag), the two year-old-daughter of Zara and Mike Tindall; Savannah (third right), 5, and Isla Phillips (right), 3, daughters of The Queen's eldest grandson Peter Phillips and his wife Autumn; Prince George (second right), 2, and in The Queen's arms and in the tradition of Royal portraiture, the youngest great-grandchild, Princess Charlotte (11 months), children of The Duke and Duchess of Cambridge, in this official photograph, released by Buckingham Palace to mark her 90th birthday April 20, 2016 Credit must read: c2016 Annie Leibovitz/Handout

LONDON (Reuters) - The value of the British monarchy stands at around $84 billion, according to a report released on Thursday as Queen Elizabeth marked her 90th birthday.

Consultancy Brand Finance estimated the figure of 58.4 billion pounds by adding 21 billion pounds of tangible assets like the Royal Collection treasure trove, private estates and the Crown Estate to 37.4 billion pounds of intangible assets, namely the monarchy's long term contribution to the economy.

It said the royal family contributed more than a billion pounds to the British economy, adding value to areas such as tourism and business.

"It's like a giant PR campaign for the UK," Brand Finance Chief Executive David Haigh told Reuters.

Brand Finance calculated the contributions by netting off security, palace maintenance and the Sovereign Grant -- the queen's public income -- against income sources including "uplift to tourism, the price premium commanded by brands with royal warrants and the surplus generated by the Crown Estate".

Estimates of the British monarchy's wealth are complicated as some assets are privately owned and others like the Crown Estate are owned by the queen on behalf of the nation.

Anti-royalists have provided their own figures and dispute claims the royal family boosts tourism.

Last year, campaign group Republic published a report saying "each 'working royal' costs the taxpayer an average of 18.5 million pounds, making them the most expensive public officials in the country". ($1 = 0.6974 pounds)

(Reporting By Marie-Louise Gumuchian; additional reporting by Hayley Platt)