What is a billion?

Tell a man that there are 400 billion stars and he'll believe you. Tell him a bench has wet paint and he has to touch it to make sure.

We use the word billion so unhesitatingly in the English language, without thinking that a billion is something too huge for most of us to comprehend.

Place a billion 1-dollar notes end to end, and they'll reach the Moon and back two thousand times!

That's not a very useful fact, and it would seem a poor use of money anyway. But it does illustrate that a billion is a really big number.

The following is based on the standard international definition of the word billion, which is one thousand-million (10⁹ = 1,000,000,000).

You might have started reading this page around 30 seconds ago. Can you guess how long ago one billion seconds was?

A billion seconds ago was 11:04 AM Monday 15th of March 1993. (Were you alive one billion seconds ago?)
A billion minutes ago takes us back to the days of the Roman Empire - 123 AD.
A billion hours ago was 112,053 BC, when our Neanderthal predecessors were hunting mammoth.
A billion dollars ago was less than 12 hours, at the rate Washington spends taxpayers' money to kill people (source ) That's $24,670 every second!

So when we talk in these webpages about a billion, we really mean a number that's

The prefix used for billion is giga- (a gigabyte is one billion bytes ) and is derived from the Greek γιγας, meaning gigantic.

The original meaning of the word billion is a bit complex.

The prefix bi- means two, and the suffix -illion comes from the word million. But the origin of million itself is obscure. The prefix milli- means thousand and the Old French word million just meant a very big thousand. In those days, counting so many thousands of anything was not common and people had little interest in identifying large numbers so precisely.

The original French billion was therefore million² (million x million; i.e. 10¹²) and was adopted by other European countries, notably England and Germany, and spread around the world through European colonialisation. Later, Italian and French scientists and academics realised that this huge number had no practical use, and modified the definition to a thousand-million (10⁹).

Britain and Germany retained the original definition, and it was at this time that America chose the French definition (10⁹), along with many other French-rather-than-British influences after the American Revolution War.

For compatibility with its European neighbours, Italy and France reverted to million-million in 1948. But some thirty years later in Britain, thousand-million was adopted as the official billion for government statistics.

So what is the correct definition of billion?

Well, in many cases, both million and billion have the same meaning. That is, a huge number that most human minds cannot comprehend. So you can safely use either.
Or if you want to show off, you could use the word milliard, which means a thousand-million.
However, if you want to be precise and avoid any misunderstanding, it's best to avoid the word altogether and say 'thousand-million' or 'million-million'. Otherwise, as a gentleman named Alastair kindly pointed out to us recently, you run the risk of being over-charged for something: a US billion is worth only 0.1% of a European billion!

Before the White House stopped showing military spending, the US Government factsheet showed the US defense budget for 2015 was $598.5bn. This excluded nuclear weapons research and production, and also excluded the wars in Afghanistan and Iraq ($159.3bn budgeted for 2011). By 2018 the figure had risen to $643.3 and by 2020 to $778bn ($24,670 per second). Source IISS.

We all know that the USA's longest war in history was in Afghanistan. After 20 years, the cost of that war came to close on a trillion dollars (one thousand billion).

And the result of all that was 3,500 coalition deaths (that's more than the number killed in the 11 September 2001 attacks), plus 64,100 Afghan military and police deaths and 111,000 civilians deaths. Further, hundreds of thousands of survivors will continue to suffer injuries for the rest of their lives.

You and I pay for that destruction of life and property through our taxes. We all know that, but have you considered who actually receives that money?

The United Nations Development Programme has estimated that for less than one tenth of that budget, clean water, adequate food, sanitation, and basic education could have been provided for every person on the planet. That money would not, of course, have gone into the coffers of the arms industry.

"Every gun that is made, every warship launched, every rocket fired, represents, in the final analysis, a theft from those who hunger and are not fed, who are cold and are not clothed. This world in arms is not spending money alone. It is spending the sweat of its laborers, the genius of its scientists, the hopes of its children."

Dwight D Eisenhower, 34th president of US 1953-1961

Gigabyte is often used in computing, which, unlike humans, counts in binary rather than decimal. So instead of 10⁹, giving us a nice round 1,000,000,000, the computer's gigabyte is 2³⁰, which is 1,073,741,824.

Close enough.

And we Americans have a personal understanding of 'huge'. Collectively we eat 10 billion doughnuts every year, and although we account for less than a twentieth of the world's population, we account for more than a third of their weight. (Source: 1,339 QI Facts To Make Your Jaw Drop by John Lloyd, John Mitchinson & James Harkin, Faber & Faber £9.99)