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18th century (typical of the crossing, 1501-1866)Primary source · 3 sourcesWell documented

The Middle Passage Kills Roughly One in Seven Who Board

Packed below deck for six to ten weeks, an estimated 1.8 million enslaved Africans die in the crossing before ever reaching the Americas

On the timeline · around 18th century (typical of the crossing, 1501-1866) · The Trade at Its Height (1700-1791)The Trade at Its Height (1700-1791)The Middle Passage Kills Roughly One in Seven Who Board1720173017401750176017701780

Quick facts

Estimated embarked
12,521,337 (Trans-Atlantic Slave Trade Database)
Estimated disembarked
10.7 million
Estimated deaths at sea
roughly 1.8 million
Typical crossing time
6-10 weeks

What happened

Enslaved Africans forced aboard slave ships were packed into spaces built to maximize the number carried rather than to keep people alive, chained below decks with barely room to turn over, for a crossing that typically took six to ten weeks. According to the Trans-Atlantic Slave Trade Database, of an estimated 12.5 million people embarked on slave ships across the trade's entire span, roughly 10.7 million disembarked alive in the Americas, meaning nearly 1.8 million died during the crossing itself. Mortality rates were highest in the sixteenth century, close to 30 percent of those embarked, and fell to below 15 percent by the trade's final decades as ship design and provisioning improved, though improvement here meant preserving profit rather than reducing suffering. Voyages to the Spanish Americas had the highest death rates of any route; voyages to Brazil had the lowest, though still close to one in eight. Disease, dehydration, suffocation, violence by crew, and suicide by captives who threw themselves overboard all contributed to the toll, and historians note that the true death toll of the trade, counting deaths during capture, the march to the coast, and the first year after arrival, was substantially higher than the deaths recorded at sea alone.

Why it matters

The Middle Passage's mortality is the single clearest measure of the trade's violence: it means the estimated 12.5 million people who were embarked understates by millions the number of Africans actually killed by the trade once capture, the coastal march, and post-arrival deaths are included. The Trans-Atlantic Slave Trade Database's voyage-by-voyage mortality figures, drawn from ship logs and insurance and customs records, are what allow historians to state this scale with precision rather than estimate.

How we know

The Trans-Atlantic Slave Trade Database compiles records from more than 36,000 individual slaving voyages, drawing on ship manifests, customs house records, and insurance documents; its published estimates of 12.5 million embarked and 10.7 million disembarked are the figures historians cite as the current scholarly consensus, understood as an estimate built from documented and inferred voyages rather than an exact count.

Sources

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Part of a timelineThe Atlantic Slave Trade29 events · Four centuries in which European traders forced an estimated 12.5 million Africans onto ships bound for the Americas, and the enslaved people, revolts, and abolitionists who fought it from the first crossing to the lastView all →