MOAB, the “mother of all bombs”: how far its blast reaches, and what it cannot reach

01 · The object

Nine metres long, and nearly all of it explosive#

The GBU-43/B Massive Ordnance Air Blast is 9.2 metres long and about a metre wide. It weighs 9.8 tonnes, and 8.5 tonnes of that is H-6, a blend of TNT, RDX and aluminium powder: 87% of its weight is explosive, an unusually thin case for a bomb.

No bomber carries it. It rides on a sled in the hold of an MC-130 transport aircraft and leaves through the open rear ramp; fins and GPS steer it down. The US Air Force Research Laboratory rushed it out for the invasion of Iraq: the first test came on 11 March 2003, days before the war began, and it was not used there. Reportedly about 15 were made; the Air Force’s mid-2000s estimate of the unit cost was about $170,000.

02 · Biggest by what?

Not the heaviest American bomb, but the one in service with the most explosive#

Headlines call it the biggest American bomb. By weight it is not. The GBU-57 bunker buster weighs 13.6 tonnes, and the T-12 of the 1950s, never used in war, almost 20. What sets MOAB apart, among the bombs in service, is how much of it explodes.

The bar under each bomb is its weight; the coloured part is explosive. The GBU-57 carries about 2.4 tonnes of explosive inside a thick steel body built to survive hitting rock: about a fifth of its weight. Britain’s Grand Slam of 1945 weighed as much as MOAB, with about half the explosive.

03 · The energy

As TNT, its blast is a block 1.9 metres on each side#

MOAB’s explosion is usually rated at 11 tonnes of TNT. Pressed into solid TNT, that is a cube 1.9 m on each side, taller than the person beside it.

The rating is approximate. NATO’s tables count H-6 as 1.38 times TNT for peak pressure and 1.15 times for impulse, so the same 8.5 tonnes are worth 9.8 to 11.7 tonnes of TNT depending on what is measured. This page uses 11.

The ladder · 1

Beirut 2020 was about 45 MOABs#

In January 1917 a TNT works at Silvertown in east London blew up: about 50 tonnes of explosive, roughly 4.5 MOABs, 73 people killed. In August 2020 ammonium nitrate stored in the port of Beirut exploded. From 16 videos, Rigby and colleagues estimated 0.5 kilotons of TNT, with an upper limit of 1.12: about 45 MOABs, a cube 6.7 m on a side.

The ladder · 2

Hiroshima: about 1,400 MOABs, from a bomb half its weight#

Little Boy weighed 4.4 tonnes, less than half of MOAB, and released about 15 kilotons, give or take 20%: some 1,400 MOABs. Its TNT would be a cube 21 m high, the height of a seven-storey building. “Mother of all bombs” describes the top of the non-nuclear scale; the bottom of the nuclear one starts far above it.

The ladder · 3

Tsar Bomba, 1961: a cube as tall as the Eiffel Tower#

The largest bomb ever exploded, the Soviet Tsar Bomba, released about 50 megatons: 4.5 million MOABs. As TNT it would be a cube 310 m high, close to the Eiffel Tower’s 330 m. The red dot at the foot of the tower is MOAB’s cube.

04 · The blast

What MOAB’s blast does to the houses around it#

MOAB is set to burst about 1.8 m above the ground, according to DW. The shock spreads as a dome. The rings here come from a formula British engineers derived from data on brick houses bombed in the Second World War, revised in 1994 to allow for energy taken up by a casing, and printed in the UN’s ammunition guidelines:

• about 100 mbrick houses demolished
• about 140 mdamaged beyond repair
• about 250 muninhabitable, needing extensive work
• about 430 muninhabitable until repaired
• about 850 mhabitable, but ceilings, tiles and glass need repair

The coloured line shows how far the shock front has travelled, in real time: about 2.7 seconds to reach a kilometre.

05 · One kilometre

At a kilometre, broken windows#

Al Jazeera, reporting the view of a military analyst on 15 October, wrote that the blast would destroy everything above ground within a kilometre. The measurements behind the blast tables do not support that. At 1 km the peak overpressure is about 2 kPa, a fiftieth of normal air pressure. That breaks windows, and flying glass injures people; walls stand.

The pressure usually taken to wreck a house, 5 psi or 34 kPa, is reached about 130 m from the burst. In Achin in 2017, imagery analysts at Alcis counted 38 buildings and 69 trees destroyed within about 150 m, and added that much of the damage appeared to come from ground fighting.

06 · Underground

How deep it reaches: zero metres#

Everything MOAB does happens in the air. It explodes before it touches anything and leaves little crater: at Achin the BBC found “no big crater”, and an Afghan officer pointed to green trees still standing 100 m away. The blast presses on the ground; it does not dig into it.

The American bomb built for buried targets is the GBU-57. Its steel body is designed “to penetrate up to 200 feet underground before exploding”, about 61 m, in the US Air Force’s words, which do not say through what. On 22 June 2025 (Iran time) seven B-2s dropped 14 of them on Iran, a dozen on Fordow, their first use in war.

Fordow’s halls are reported to lie at least 80 m down. The tunnels at Pickaxe Mountain near Natanz, named in the new plans, were estimated in 2023 from the rock dug out at 80 to 100 m; digging has continued since. These depths are public estimates, drawn as bands.