A billion is a thousand million: 1,000,000,000, with nine zeros. A trillion is a thousand billion: 1,000,000,000,000, with twelve zeros. Each step up multiplies by a thousand. The scale is easy to underestimate — a billion seconds is about 32 years, while a trillion seconds is about 32,000 years.
The numbers
- million — 1,000,000 (six zeros)
- billion — 1,000,000,000 (nine zeros)
- trillion — 1,000,000,000,000 (twelve zeros)
Each step multiplies by one thousand, so a trillion is a thousand billion and a million million.
Why the gap is hard to feel
The words are similar in length and rhythm, which flattens a difference of a thousand times. Seconds make it concrete: a million seconds is about eleven and a half days; a billion seconds is roughly 32 years; a trillion seconds is roughly 32,000 years.
The older British billion
Britain once used a "long scale" in which a billion meant a million million — what is now called a trillion. That usage was official until 1974 and has since been abandoned; British and American English now agree. It is worth knowing only when reading older British sources, where a billion may mean something a thousand times larger than it does today.
Frequently asked questions
How many zeros are in a trillion?
Twelve. A trillion is written 1,000,000,000,000 — a thousand billion, or a million million.
How many billions are in a trillion?
One thousand. Each step from million to billion to trillion multiplies by a thousand.
Did a billion once mean something different in Britain?
Yes. Under the older long scale a British billion meant a million million. That changed officially in 1974, and British usage now matches American usage.