The actor, the latest reincarnation of the time-travelling science-fiction hero, will be joined at an event in Cardiff by co-star Jenna Coleman and show supremo Steven Moffat before being whisked off to London on the same day.
They will then go on to visit five continents in 12 days, calling in at seven cities, ahead of the launch of the new series, Capaldi's first as The Doctor.
The tour ends in Rio de Janeiro in Brazil on August 19. Along the route it will call in to South Korea, Australia, the US and Mexico.
Fans saw Capaldi become the latest regeneration of the Doctor at Christmas and he has spent the past few months working on his first full series, starring alongside Coleman who returns as assistant Clara.
Show bosses say it is the largest promotional tour undertaken for the show which is seen around the world and is on a high after its 50th anniversary celebrations last year. A special episode, The Day of the Doctor, was broadcast in 98 countries simultaneously and was seen in more than 1,500 cinemas.
Capaldi said: "It's fantastic that so many people across the world love Doctor Who. After eight months solid filming deep in the world of monsters, Jenna and I are thrilled to be heading for the planet of fans."
The first feature-length edition of the new series, called Deep Breath, will be beamed into screens around the globe from August 23 to allow fans to share the moment as Capaldi takes on the role of The Doctor.
The first episode is set in Victorian London and will feature familiar characters Madame Vastra (Neve McIntosh), Jenny Flint (Catrin Stewart) and Strax (Dan Starkey).