No one but the Holy Spirit knows for certain who will come out of the conclave as the next Successor of Peter -- and that means the Vatican staff has to be prepared for anyone to take on the signs of the office.
The white papal garments are provided in three different sizes. Even then, the garments won’t be a perfect fit, but one of them should be sufficient for a first appearance.
After all, the variation in height alone could make a big difference in size. Anecdotally, the shortest pope was supposedly just 5’1” (Pope Pius IX, 1846 to 1878). Interestingly, the Church doesn't have a tall pope on record. The tallest we know of was St. Pope John Paul II, who sources say was about 5’10’’.
Traditionally, along with the white cassocks, shoulder capes (mozette), and sashes, the pope-elect is given the opportunity to wear red shoes, available in several sizes as well. The red is symbolic of the blood of the martyrs and has been a custom since the relatively early days of the Church. After initially choosing a pair that is a close-enough fit, the pope will then decide whether to keep the shoes or replace them with others, as well as fit them for things like orthotics, etc, if needed!
Pope Francis surprised everyone by keeping the same shoes he was wearing, a decision he is said to have attributed to them being orthopedic shoes. However, many also saw his shoe choice as a symbol of wanting to live simply.
A white overcoat is generally also on the papal wardrobe initial checklist. However, given the warm weather in Rome at this time of year, it's likely that it doesn't need to be ready until later!
And naturally, there will be a variety of sizes of zucchettos -- the skull caps that resemble those of bishops and cardinals, except in white.
All of these garments will be waiting in the Room of Tears, a small room adjacent to the Sistine Chapel. Once the pope has been chosen and has given his acceptance, he has some time in this room to dress, to reflect, and -- naturally -- to pray (perhaps with tears).
There in the room, a gold stole will also be waiting, but the pope will not put it on right away. Instead, he will step out onto the balcony of St. Peter’s and be introduced with his baptismal name, and then his new chosen papal (or “regnal”) name. After that, the stole will be placed on him and he will face the people in St. Peter’s Square and around the world to give his first “Urbi et Orbi” (to the city and the world) blessing.
