How many years old is the universe?
Guess before you scroll — the answer is below
The answer
13,800,000,000 years
Roughly 13.8B.
The universe is about 13.8 billion years old, measured from the cosmic microwave background — the leftover heat of the Big Bang, still detectable in every direction. The margin of error on that figure is under 1%.
How to get close to this number
Anchor on the Earth. This site's companion question puts the planet at around four and a half billion years, and the Earth formed well into cosmic history rather than at its start. A universe roughly three times the age of the Earth is the right relationship.
The measurement method is the part worth knowing: the age comes from the cosmic microwave background, the leftover heat of the Big Bang, still detectable in every direction. Precise measurements of tiny temperature variations in that radiation constrain the age, and they do it to within one percent.
That precision is the genuinely remarkable claim. A margin of error under one percent on the age of everything is better than the precision available for many historical dates within the last few thousand years, and it comes from a measurement of faint microwave radiation rather than from anything we can touch.
Where this number comes from
| Source | ESA Planck mission / NASA |
|---|---|
| Figure refers to | 2024 |
| Last checked | |
| Unit | years |
Numbers move. If this one has drifted from its source, let us know.
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