History · IN60SECONDS

Why did the Titanic sink so fast?

The iceberg opened at least five, and likely six, of its watertight compartments, more than the ship could survive. Water then spilled over the too-short bulkheads, and it sank in 2 hours 40 minutes.

Quick Answer

Titanic hit an iceberg at 11:40 p.m. on April 14, 1912, and sank at 2:20 a.m., just 2 hours and 40 minutes later. Its hull was divided into watertight compartments, and it was designed to stay afloat with up to four of them flooded. The iceberg scraped along the starboard side below the waterline and opened at least five compartments; Britain’s 1912 inquiry found damage in six. As the bow filled and sank lower, water spilled over the tops of the bulkheads, which reached only as high as E or D deck, into the next compartment, then the next. Sonar surveys in 1996 showed the damage was surprisingly small: six narrow openings totaling about 12 square feet. Metallurgists at the U.S. National Institute of Standards and Technology later found that many of the ship’s wrought-iron rivets contained high levels of slag, which may have helped the seams pop open. About 1,500 of the roughly 2,224 people aboard died.

By the Numbers

2 h 40 minFrom hitting the iceberg to sinking

5–6Watertight compartments opened: at least 5, likely 6. It could survive 4

~12 sq ftTotal size of the six narrow openings found by sonar in 1996

1,178Lifeboat seats for roughly 2,224 people aboard

Key Facts

Time to sink: 2 hours 40 minutes, from 11:40 p.m. to 2:20 a.m.
Built to survive: Up to 4 flooded compartments. The iceberg opened at least 5, likely 6
The fatal flaw: The bulkheads weren’t tall enough, so water spilled from one compartment to the next
Deaths: About 1,500 of the roughly 2,224 people aboard

How the flooding spread

The iceberg opens at least five compartments
It scrapes along the starboard side below the waterline, opening narrow gaps in the hull.
The bow sinks lower
The weight of the water pulls the front of the ship down.
Water spills over the walls
The bulkheads stopped at E or D deck, so water poured over their tops into the next compartment, then the next.
The ship breaks apart
The stern rises, the hull breaks in two, and Titanic sinks at 2:20 a.m.

Built to survive vs. what happened

	Designed for	April 14, 1912
Flooded compartments	Up to 4	At least 5, likely 6, then more as water spilled over
Bulkheads	Watertight walls up to E or D deck	Water poured over the tops as the bow sank
Lifeboats	20 boats with 1,178 seats	About 2,224 people aboard

Small damage in the worst place

The iceberg didn’t rip a giant gash. Sonar surveys in 1996 found six narrow openings where hull plates had buckled and separated, totaling only about 12 square feet. The problem was that they were spread across at least five compartments, and likely six, more than the ship could survive.

Walls that were too short

Titanic’s watertight compartments were sealed at the sides and bottom but open at the top. As the bow sank, water rose over each bulkhead and into the next compartment, so the flooding couldn’t be stopped.

Were weak rivets to blame?

Metallurgists at the National Institute of Standards and Technology examined rivets from the wreck and found many held about three times the ideal amount of slag, a glassy impurity that weakens iron. That may have helped the seams open. Not every expert agrees on how much it mattered.

Found in two pieces

In 1985, a team led by Robert Ballard found the wreck more than two miles down, broken in two, confirming that the ship split apart as it sank.

Myth vs. Fact

MythThe iceberg tore a huge gash in the hull.

FactSonar found six narrow openings totaling about 12 square feet.

MythThe watertight compartments were fully sealed.

FactThey were open at the top, so water spilled over them as the bow sank.

The Bottom Line

Titanic sank fast because the iceberg opened more compartments than it could survive, and its bulkheads were too short to stop the water spreading. Small openings in the worst possible place doomed it in under three hours.

Correction

September 27, 2026: An earlier version of this story said the iceberg opened five watertight compartments. Sources differ: at least five were breached, and Britain’s 1912 inquiry found damage in six. We updated the summary, Quick Answer, Key Facts, By the Numbers, comparison table and flooding steps, and added the inquiry report to the sources.

Read our corrections policy.