Pippa Middleton
Pippa Middleton, the sister of Britain's Catherine, Duchess of Cambridge, watches the women's singles tennis match between Angelique Kerber of Germany and Heather Watson of Britain at the Wimbledon Tennis Championships, in centre court, London June 26, 2014. Reuters/Max Rossi

Duchess of Cambridge Kate Middleton's sister Pippa Middleton is getting married to hedge fund manager James Matthews on May 20. There has been speculation in the media that the royal sister will spend US$320,113 (AU$436153.96) for the wedding, which will be attended by her sister, Prince William and their two kids Prince George and Princess Charlotte.

According to Bridebook, a British wedding magazine, the budget for Pippa and Matthews' wedding is almost fifteen times the cost of a normal wedding. May 20 is expected to be a busy day for getting hitched in the United Kingdom, as approximately 5,000 couples are getting married on that day. The website has segregated the costs of their wedding according to the money spent on the venue, cake, food, dresses, etc.

Around 350 guests are expected to attend the event, which is to take place at the home of the Middletons, but due to unexpected rain, the family may have invested in rain-proof arrangements. According to Vogue, Pippa has asked her guests to carry two outfits. Since the ceremony will take place in a church, the other attire might be required for the reception at the Middleton home.

Meanwhile, Pippa is expected to wear a custom wedding gown by designer Giles Deacon, the cost of which is estimated to be at five figures. Deacon is a London-based fashion designer best known for his playful designs and collaborations, especially with High Street retailer New Look. The speculation about him designing the gown for Pippa surfaced when Deacon was spotted leaving the royal's house carrying a pile of garment bags.

Deacon previously designed Abbey Clancy’s wedding gown when she tied the knot with British footballer Peter Crouch. The cost of Pippa's gown, meanwhile, is estimated to be at around US$13,000 (AU$17,703.94). The bride-to-be has also ordered a bridal flap or veil from milliner Stephen Jones, and it may cost around US$2,590 (AU$3527.17).

Other fashion designers Pippa may be considering for her wedding are Suzanne Neville, Jenny Packham, Emilia Wickstead and Alexander McQueen. Her sister chose McQueen to design her wedding gown when she got married to Prince William. During that wedding, Pippa's mermaid-style gown also became an instant hit.

Prince George and Princess Charlotte will be the highlights of Pippa Middleton's wedding as the two are due to be flower girl and page boy. Their outfits will reportedly be provided by Nicki Macfarlane, who was also responsible for designing the flower girl outfits for the royal wedding. Stay tuned for more wedding updates.