Tsar Bomba: The Largest Nuclear Bomb Ever Detonated

Tsar Bomba, officially the RDS-220, was a Soviet hydrogen bomb detonated on 30 October 1961 over Novaya Zemlya in the Arctic. Its yield was about 50 megatons of TNT, roughly 3,300 times the Hiroshima bomb, and it remains the largest nuclear explosion ever carried out. It was designed for 100 megatons, but its builders cut the yield in half to limit radioactive fallout. Friday, 30 October 2026, is the 65th anniversary of the test.

This guide covers how the bomb was built and dropped, how far its effects reached, how it compares with other weapons, and why nobody ever built another. Technical figures follow the Nuclear Weapon Archive, which compiles Russian accounts, and we flag where estimates differ.

Tsar Bomba at a Glance

The Soviet Union announced a 50-megaton figure at the time, and that is the number usually quoted. Because the explosion was measured by instruments and seismic stations rather than a published test report, you will see estimates above and below it.

Why the Soviet Union Built It

In 1961 the Cold War was at one of its worst moments. The Berlin Wall went up in August, and in September Moscow ended a three-year unofficial pause in nuclear testing and began a large test series. Nikita Khrushchev wanted a demonstration the world could not ignore. He told the 22nd Party Congress in October that the Soviet Union would test a 50-megaton bomb, and the bomb that followed was as much a political signal as a weapon. Our guide to who has nuclear weapons shows how that rivalry grew into today's arsenals.

The device was a three-stage design: a fission bomb set off a fusion stage, which in turn drove a second fusion stage. Calculations showed that with a uranium tamper it would reach about 100 megatons. The designers swapped in lead, which cut the yield to about 50 and meant that almost all of the energy came from fusion rather than dirty fission. That choice kept the fallout far below what a 100-megaton burst would have produced.

How the Bomb Was Dropped

The weapon was too big for any bomber to carry normally. A Tu-95 had to be rebuilt as the Tu-95V: the bomb bay doors were removed, the fuselage fittings were changed to hold the bomb, and the aircraft was painted white to reflect the heat of the flash. A Tu-16 flew nearby to film and measure the blast.

On the morning of 30 October the Tu-95V, commanded by Maj. Andrei Durnovtsev, released the bomb from about 10,500 meters. A large parachute slowed it so that the aircraft could get roughly 45 kilometers away before it went off. Both aircraft survived. Durnovtsev was later named a Hero of the Soviet Union.

Sakharov and the Aftermath

Andrei Sakharov, one of the physicists behind the Soviet hydrogen bomb, spent the years after the test turning against atmospheric testing. He had warned earlier about the health damage caused by fallout, and in his memoirs he wrote that he pressed for the test ban treaty. He went on to become one of the Soviet Union's best-known dissidents and won the Nobel Peace Prize in 1975.

The test did not make the world safer in the short run. A year later came the Cuban missile crisis, which brought the two superpowers closer to nuclear war than at any other point. Both governments then agreed to move their tests out of the atmosphere, which led to the 1963 treaty.

Tsar Bomba Effects: How Far Did the Blast Reach?

The effects below are the commonly reported figures. The test site was remote, so many are estimates drawn from observers and instruments rather than measured damage.

Because the bomb exploded in the air, not on the ground, it threw up relatively little radioactive debris compared with a ground burst of the same size, and the fireball did not scoop out a crater.

Tsar Bomba vs Hiroshima, Castle Bravo and Modern Warheads

Megatons are easy to say and hard to picture. This table puts Tsar Bomba beside the weapons most often compared with it.

Yields for modern warheads are from SIPRI's 2026 Yearbook and U.S. government fact sheets. Castle Bravo, tested at Bikini Atoll on 1 March 1954, was the biggest American test. It yielded 15 megatons, far more than the 6 its designers had expected, and its fallout spread over inhabited islands and a Japanese fishing boat. Tsar Bomba was still more than three times bigger.

Was Tsar Bomba Ever a Real Weapon?

No. It was a one-off test of what was possible, and it was never deployed. The bomb weighed about 27 tons, and the Tu-95 could barely lift it. The bomber would have had to fly into the enemy's air defenses to deliver it and would probably not have survived. A 100-megaton version would have been even less practical, with fallout that would have been much harder to contain.

There was a military logic against it too. A single huge explosion destroys one place completely, but it wastes energy: much of the energy goes into destroying ground that is already destroyed. Several smaller warheads on separate missiles destroy more targets for less weight. A casing of a similar bomb is displayed at the nuclear weapons museum in Sarov.

Why Nobody Built Another Giant Bomb

Missiles settled the question. Intercontinental ballistic missiles were becoming the main way to deliver warheads, and they could carry only a limited weight. Weapons designers instead made warheads smaller and more accurate, then put several on one missile. Most warheads in service today are measured in hundreds of kilotons, and even the biggest are in the low megatons, a small fraction of Tsar Bomba's.

Politics closed the door as well. The United States, the Soviet Union and Britain signed the Partial Test Ban Treaty in August 1963, which banned nuclear tests in the atmosphere, in space and under water. A 50-megaton blast was out of the question after that.

Tsar Bomba Today: Nuclear Testing Back in the News

Russia last carried out an explosive nuclear test at Novaya Zemlya in October 1990, according to the Center for Strategic and International Studies (CSIS). The site has been in the headlines again. A year ago this week, Donald Trump ordered the Pentagon to start testing nuclear weapons on an equal basis with other countries. In November 2025 Vladimir Putin asked his officials for proposals on preparing for tests, and Russian officials have said the site could resume work quickly. Chief of the General Staff Valery Gerasimov put the preparation time at several months to several years, CSIS notes.

No explosive test has followed, and the arms control framework is thinner than it was. The last treaty limiting U.S. and Russian arsenals, New START, expired on 5 February 2026. Russia's newest headline weapons are about delivery, not size, such as the nuclear-powered Burevestnik cruise missile tested in October 2025 and the Poseidon torpedo covered in our guide to Russian submarines.

FAQ: How Big Was Tsar Bomba?

About 50 megatons of TNT, according to the figure usually cited. That is roughly 3,300 times the Hiroshima bomb, or about 10 times all the explosives used in World War II, by the commonly quoted comparison.

Where and When Was Tsar Bomba Tested?

Over the Mityushikha Bay area of Novaya Zemlya, an Arctic archipelago in northern Russia, on 30 October 1961.

Could Tsar Bomba Have Been Bigger?

Yes. The design could produce about 100 megatons with a uranium tamper. The Soviet team used lead instead, halving the yield and the fallout.

Did the Bomber Crew Survive?

Yes. The Tu-95V dropped the bomb from 10,500 meters and got about 45 kilometers away before the blast. Its commander, Maj. Andrei Durnovtsev, was later named a Hero of the Soviet Union.

Is Tsar Bomba Still the Largest Bomb Ever?

Yes. It is the largest nuclear weapon ever detonated, and no country has built a larger one. Most warheads in service today are measured in hundreds of kilotons, and even the biggest are in the low megatons.