Nuclear Yield/Weight Ratios

(Updated 25 December 2011)


US Nuclear Weapons: The Secret History by Chuck Hansen
Cary Sublette's Nuclear Weapons Archive

Fissionable Fuels


Oralloy (Oak Ridge Alloy)
(93.5% Enriched U-235)

Plutonium 239


$53/gram (1996)
$53,000/kg (1996)

$4.65/milligram (1998; 99%+)
$4.65 million/kg (1998; 99.9%+)

Energy Release from 100% Efficient Reaction

17 kt/kg

20 kt/kg

Minimum Critical Mass

14.1 to 13.5 kg
(10 cm Beryllium Reflector)

4.4 kg
(10 cm Natural Uranium Reflector)


18.8 g/cm3

19.7 g/cm3


Silvery-Gray Metal.

Silvery-White Metal.

Produces 2.4 W/kg of heat from radioactive decay, so special precautions must be taken in design of devices to avoid self-generated heat from ruining them.

Fusionable Fuels


Liquid Deuterium





$1.30/gram (1997; 95-96%)

$6.70/gram (1997; 99%)

Energy Release from 100% Efficient Reaction

82.2 kt/kg

64 kt/kg

40.3 kt/kg


0.169 g/cm3

0.534 g/cm3

0.534 g/cm3


Cryogenic Fuel.

Whitish, slightly blue powdery light salt.

Is pressed into a ceramic and then machined into shapes as necessary for devices.

Known Nuclear Weapon Yield/Weight Ratios

Mark One (Little Boy) – A plug consisting of 25.2 kilograms (42% of the critical mass) was fired into a series of concentric rings containing the remaining 58% (34.8 kilograms) of the critical mass. About 700 grams completely fissioned out of a total of 60 kilograms of Uranium-235, for a efficiency of 1.2% and a yield/weight ratio of 0.23 kt/kg.
Model 1561 (Fat Man) – A sub-critical mass of 6.2 kilograms of Plutonium was “squeezed” by a complex series of explosive detonations into a critical mass. Of 6.2 kilograms of Plutonium, about 1.3 kilograms fissioned completely, for an efficiency of 21% and a yield/weight ratio of 2.8 kt/kg.

Known U.S. Nuclear Physics Package Weights

W76 (Trident I/II): 100 kT in 362 lbs
W80 (ALCM/ACM): 5 to 150 kT in 290 lbs
W84 (BGM-109G): 0.2 to 150 kT in 388 lbs
W85 (Pershing II): 5 to 80 kT in 880 lbs
W87 (MX): 300 kT in 440-660 lbs
W89 (SRAM II): 200 kT in 324 lbs

1980s U.S. Nuclear Physics Package Yield/Weight Calculator

Notes: Based on the yields/weights given above (excluding the W85); do not use this equation for anything below about 75 kilotons to be on the safe side.
Weight = 46.308 * Yield0.406
Weight is in Pounds
Yield is in Kilotons