Why did many slaves die during the Middle Passage voyage from Africa to the Americas?
Matthew White estimates 10 to 15% of 10 to 12 million slaves transported across the Atlantic died. The main cause of death was disease.
So 1 to 1.5 million on the actual voyage. Many died being captured and many died after arrival in the Americas. Most slaves that were transported ended up in Brazil. The 1700s saw the biggest numbers transported. The time period was from about 1450 to 1807. Total death toll overall about 16 million.
The death toll of sailors on the ships was about the same. White suggests that this shows how badly the sailors were treated rather than how well the Slaves were.