How Deep Is the Ocean? Average Depth, Challenger Deep and Everest

The ocean’s average depth is 3,682 meters (12,080 feet), and its deepest known point, the Challenger Deep in the Mariana Trench, is about 10,935 meters (35,876 feet) down, according to NOAA. That is deeper than Mount Everest is tall: drop Everest into the trench and its summit would still sit about 2 kilometers (1.3 miles) underwater.

Picture standing on a ship over the Challenger Deep. Below the hull there is almost 11 kilometers of water, roughly the cruising height of a jet airliner, but in the other direction. Sunlight fades out in the first few hundred meters. Everything below that is dark, cold and under enormous pressure.

How deep is the ocean on average?

NOAA’s National Ocean Service puts the average ocean depth at 3,682 meters (12,080 feet), a little over 2 miles. Most of the seafloor is not near the coast. Beyond the continental shelves and slopes, the ocean floor flattens into vast abyssal plains several kilometers down, broken by mid-ocean ridges, seamounts and trenches.

The shallow edges are a small share of the total. That is why the average is so deep even though beaches and coastal waters are what most people see.

Where is the deepest point in the ocean?

The deepest known point is the Challenger Deep, at the southern end of the Mariana Trench in the western Pacific Ocean, several hundred kilometers southwest of Guam. NOAA’s National Ocean Service gives its depth as approximately 10,935 meters (35,876 feet).

You will see slightly different numbers in different sources. NOAA’s JetStream ocean pages, for example, give 10,994 meters (36,070 feet). Depth figures for the trench come from separate surveys with different instruments and corrections, so treat the Challenger Deep as roughly 10,900 to 11,000 meters deep rather than an exact figure.

How does the ocean compare with Mount Everest?

The Challenger Deep is about 2 kilometers deeper than Everest is tall. China and Nepal jointly announced Everest’s height as 8,848.86 meters (29,032 feet) in December 2020.

NOAA divides the water column into five zones by depth, described on its layers of the ocean page: the sunlight zone, the twilight zone, the midnight zone, the abyssal zone and the hadal zone in the trenches. Life is found in all of them. Our guide to what lives in the deep sea covers the animals at each level, and many of them make their own light, as explained in our article on bioluminescent animals.

How do scientists measure ocean depth?

Scientists measure ocean depth mainly with sonar. A ship sends a pulse of sound toward the seafloor and times how long the echo takes to return. Because the speed of sound in seawater is known, and corrected for temperature and salinity, the travel time gives the depth.

• Single-beam echo sounders measure one point directly below the ship. Older charts are built mostly from these lines of soundings.
• Multibeam sonar sends a fan of beams and maps a wide strip of seafloor on each pass, producing detailed 3D maps.
• Satellites cannot see the seafloor, but they measure tiny bumps and dips in the sea surface caused by the gravity of mountains and trenches below. That gives a global but much coarser picture.

Uncrewed vehicles and deep-diving landers add direct measurements in places like the trenches, which is part of why depth figures for the Challenger Deep keep being refined.

How much of the seafloor has been mapped?

As of April 2026, 28.7% of the global seafloor had been mapped with modern high-resolution sonar, according to NOAA Ocean Exploration and the Nippon Foundation-GEBCO Seabed 2030 Project. The project aims to map the entire ocean floor by 2030. About 56% of the seafloor beneath US waters has been mapped to modern standards, NOAA says.

Seeing is a different matter. NOAA estimates that less than 0.001% of the deep seafloor has actually been observed by explorers, whether through cameras, robots or crewed submersibles. The rest is known only from sonar and satellite data.

How many people have been to the bottom of the ocean?

Only a small number of people have reached the Challenger Deep. The first were Don Walsh and Jacques Piccard, who descended in the US Navy bathyscaphe Trieste on Jan. 23, 1960, a dive the Office of Naval Research still marks as a milestone. The next crewed visit came more than 50 years later.

In March 2012 filmmaker James Cameron piloted the one-person submersible DEEPSEA CHALLENGER to the bottom, the first crewed visit since 1960, according to Woods Hole Oceanographic Institution, which now holds the vehicle. Later dives by other submersibles have added more names, but the list is still short. Getting there requires a hull that can withstand the pressure at nearly 11 kilometers, and only a few vehicles in the world have been built for it.

Bottom line

The ocean averages about 3.7 kilometers (2.3 miles) deep, and the Challenger Deep plunges to roughly 10.9 kilometers (6.8 miles), more than Everest’s height. Less than a third of the seafloor has been mapped in detail as of 2026, and only a tiny fraction has ever been seen directly.

FAQ

Which ocean has the deepest point?

The Pacific. The Challenger Deep, at the southern end of the Mariana Trench in the western Pacific, is the deepest known point on Earth.

Is the Challenger Deep exactly 10,935 meters deep?

No single figure is final. NOAA’s Ocean Service uses about 10,935 meters, other NOAA pages use 10,994 meters, and each new survey refines the number slightly.

Why is so little of the ocean floor mapped?

Detailed mapping needs a ship with multibeam sonar to pass over each strip of seafloor, and the deep ocean is vast and remote. Satellites help fill gaps but at far lower resolution.

Can a giant wave form in the deep ocean?

Tsunami waves travel fast and low across deep water and only grow tall near shore. Our explainer on how tsunamis form covers why depth matters.