The Hiroshima-Equivalent: A Modest Proposal

by Alex Wellerstein, published June 7th, 2013

Given that the media community seems to love comparing all manners of energy release to Hiroshima, no matter how inappropriate, I humbly propose a new scientific unit: the Hiroshima-equivalent, abbreviated as H-e.

Hiroshima damage map

The Hiroshima-equivalent has been pegged at exactly 15 kilotons of TNT,1 which is itself defined as being equivalent to 62.76 terajoules, or 15 teracalories.

One of the many benefits of using the H-e is that one can apply it to any type of energy release, not simply things physically similar to atomic bombs. Indeed, one should not, in any way, worry about whether the phenomena one is applying it to is anything like the actual bombings of Hiroshima. The H-e is in no way logically connected to blast phenomena, heat phenomena, ionizing radiation, radioactive fallout, or deaths upwards of a hundred thousand people. It can be applied to situations involving energy releases that occur over vastly larger areas of time and space, and in situations where only handful of people are hurt or injured. What is important about using the H-e is that you use it in a way that grabs the attention of your readers who are, as you know, bored, inattentive, and continually distracted by a multitude of empty facts, bad television, and meaningless digital social interactions.

In order to facilitate easy adoption of the Hiroshima-equivalent scale, I've created a simple calculator below. Here you can plug in a number of different types of energy expressions and find out their Hiroshima-equivalents. Precise energy measurements, such as Joules or Kilowatt-hours or Kilocalories, have that boring, "professional" feel to them, and as such are much less interesting than their Hiroshima-equivalent values.

(The above calculator is embedded in a frame; if you cannot see it, click here to open it as a separate window.)

Because sometimes energy releases are too small to be considered in unit multiples of Hiroshima-equivalents, I have, naturally, also created metric prefixes of milli-Hiroshima-equivalents (.001 H-e), micro-Hiroshima-equivalents (.000001 H-e), and nano-Hiroshima equivalents (.000000001 H-e). I have not opted to use positive prefixes (e.g. kilo-Hiroshima-equivalents) because it is much more exciting to instead say "thousands times the size of the Hiroshima bomb," obviously.

So using this new system and calculator, some fascinating facts emerge:

  • The bomb detonated over Hiroshima was exactly 1 Hiroshima-equivalent. As one would expect, but imagine the headlines if this had been around in August 1945: "FIRST ATOMIC BOMB IS DROPPED ON JAPAN; MISSILE IS EQUAL TO ENERGY OF HIROSHIMA BOMB; TRUMAN WARNS OF A 'RAIN OF RUIN.'"
  • The Sun deposits 61.34 billion Hiroshimas worth of energy onto the Earth every year — that's 168 million Hiroshimas a day, 7 million Hiroshimas an hour, 117 thousand Hiroshimas a minute!
  • The USA uses about 24 thousand Hiroshima-equivalents worth of electricity per year!
  • The Haitian Earthquake of 2010 was equivalent to around 32 Hiroshimas! (Alas, not a new conclusion.) Note that this system doesn't work for determining the yields of underground nuclear tests, because actual nuclear weapons have more complicated energy release mechanisms when underground. (Pesky details!)
  • Each year, McDonald's sells around 26 Hiroshima-equivalents worth of Big Macs in the United States alone, 42 Hiroshima-equivalents worldwide (1 H-e = 21.4 million Big Macs)!
  • My electric bill for last month was for 4.42 micro-Hiroshima-equivalents! (Which is 126.2 nano-Hiroshima-equivalents less than this month last year!)

There are, alas, some cases in which the Hiroshima-equivalent may lose its reader stopping power. For such cases, you may use the alternative unit, the Tsar Bomba-equivalent (TB-e), which is conveniently defined as 33,300 Hiroshima-equivalents. It should be used sparingly and tastefully, along the lines of "The 2004 Indian Ocean earthquake and tsunami [released less energy] than that of Tsar Bomba, the largest nuclear weapon ever detonated."

In case it isn't clear how to use this, here are some simple instructions: Whenever there is a natural disaster, explosion, or, really, anything relating to energy that just doesn't have enough pathos, tragedy, or excitement for your average reader, call up a scientist at a university somewhere, ask them to calculate how much energy was released in the event in question. He or she will probably give you some nonsense about "Joules" or "Kilowatt hours" or "Calories." Take those meaningless numbers, paste them into the right places on the calculator, and you'll instantly know how many Hiroshima-equivalents you are talking about! You simply can't go wrong.

  1. There are lots of estimates for the size of the Hiroshima bomb. Online one can find numbers range from 12-20 kilotons of TNT. A study by Los Alamos found that the best estimate of the yield for Hiroshima was 15±3 kilotons. For the purposes of a standard unit, of course, one must simply pick a number, and 15 seems appropriate in this circumstance. I note that it is tempting to define it as the lower limit, 12 kilotons, because that would mean even more Hiroshima-equivalents for any given situation, but we must have some standards. []

10 Responses to “The Hiroshima-Equivalent: A Modest Proposal”

  1. An instant classic. I’m saving the link and posting it in the comments section of any online, over-the-top article by an “objective” reporter on nuclear energy. Thank you!

  2. […] The Hiroshima-Equivalent […]

  3. Aditya says:

    Loved it. Linked to this page on my blog – I have both geeky and journalist friends and I’m sure they’ll appreciate it! 😀

  4. Ivan says:

    Thank you, Alex!
    I am shake your hands over electronical cables and wish all the best!

    In Russia, with translation and adaptation.

  5. J B says:

    The Big Mac equivalency also allows us to put into perspective very large financial transactions.

    The recent PowerBall was 6.3 H-e. We can convert for today’s price of a Big Mac, and the original cost of the Manhattan Project ( including Trinity/Nagasaki H-e ). It turns out the Lottery achieves 107 times the H-e per dollar than the Manhattan Project. Another conclusion is that it is more cost efficient to manufacture large quantities of Big Macs than to make an actual atomic bomb.

    It is a pity that McDonalds was not founded a decade earlier. We could have ‘ended the war’ a lot cheaper with the Golden Arches of Democracy.

    Currently, the US Deficit is equivalent to 179,000 H-e. This converts to 5.36 Tsar Bomba-equivalent.

  6. kevin says:

    Hiroshima-eqivalent has entered into my lexicon. My friends thank you.

  7. Ben Johnson says:

    I’ve been out of town and I just saw this. Thank you for doing the journalistic community a great service. My daughter just did a 4th grade report on the great Utah floods of ’83. If only I would have seen this before then. Instead of “the floods destroyed the town of Thistle with the force of 200 million gallons of water” it could have been “Thistle was leveled by .5 H-e bombs”. Wonder how much water the B-29s would have had to drop on Hiroshima to have had the same effect?

  8. Linda Richards says:

    To calculate the true cost of nuclear weapons in our environment (and our bodies) I use a number from the Comprehensive Test Ban Treaty Office (CTBTO) in Vienna. It is way simpler than above, and not as universal nor as precise as above.
    But it is very important. You just add up the explosive force of all the nuclear weapons test explosions in space, underground, underwater and in the atmosphere since 1946 and divide it by the CTBTO’s estimate of the Hiroshima explosion.

    Ta da! So far, worldwide, 29,600 Hiroshimas have already occurred.

    Makes me wonder about the effects on health and climate with a different perspective for sure. Sometimes when I share this number with my students, they cry. Most people gasp.

    History is much more terrifying when explained not as by governments “more than 2000 nuclear weapons tests” but with the equivalents to Hiroshima. No matter how you figure it, thank you Alex!

  9. Martin Strand says:

    Very nice one. Though, is there any chance this might be expanded to also include eV? Many journalists are as we speak unable to write silly articles about some particles popping up at the Large Hadron Collider, comparing them to Hiroshima. Doesn’t anybody care about these poor journalists?

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