Guide
Million, billion, trillion
How much bigger a billion really is, why the word once meant two different amounts, and the clearest way to feel the gap between the three.
The gap nobody's intuition survives
A million and a billion sound like neighbours and are not. The most useful way to feel the difference is to turn them into time, because a second is a unit everybody has an intuition for.
A million seconds is about eleven and a half days. A billion seconds is about thirty-two years. A trillion seconds is longer than agriculture has existed.
Nothing about reading the words gives you that. It is a consequence of each step being a thousandfold rather than a little more, and it is why a headline figure in billions and one in millions should not be compared by eye.
Each scale, as seconds
| Scale | As a duration | In figures |
|---|---|---|
| Million | About 11½ days | Ten to the sixth. A crowd this size is a large city. |
| Billion | About 32 years | Ten to the ninth. On the short scale, which is now standard almost everywhere. |
| Trillion | About 31,700 years | Ten to the twelfth, and the point at which this catalogue stops full mathematical analysis. |
Each row is a thousand times the one above. The words differ by three letters; the amounts differ by a factor of a million from top to bottom.
Why the words run out
Past a trillion the names stop being useful, and the reason is that nobody has an intuition to attach them to. Quadrillion and quintillion are real words with fixed meanings on the short scale, and almost every reader who meets one has to stop and count zeros.
Scientific notation exists for this. Writing ten to the twenty-third rather than a hundred sextillion trades a word for an exponent, and the exponent is the part that carries the information — the difference between two large quantities is almost always a difference in their exponents rather than in their leading digits.
It is also why this catalogue records a magnitude alongside a scaled quantity. Avogadro's constant has no scale word a reader would recognise, and inventing one would make it harder to read rather than easier.
When a billion meant a million million
The word billion has meant two different amounts. On the long scale, once standard in Britain and still used across much of continental Europe, a billion was a million million — what the short scale calls a trillion. On the short scale a billion is a thousand million.
British official usage moved to the short scale in 1974, and the older meaning survives in older books and in translation. A figure in billions taken from a French or German source may not mean what an English reader assumes, and the two readings differ by a factor of a thousand.
This catalogue uses the short scale throughout, and says so, because a model that let an author pick would make the corpus disagree with itself about a word it also explains.