Hubble constant converter
Convert the expansion rate of the universe between the units cosmologists use, and see the Hubble time it implies.
That's about the same as the red-giant-branch value. Its Hubble time is 13.97 billion years.
What it means
How fast is that expansion?
The Hubble time 1/H₀ is close to, but not the same as, the age of the universe, which depends on how expansion changed over time (13.8 billion years).
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That expansion rate in every unit
Learn
Three things worth knowing
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978 ÷ H₀
Hubble time in billions of years ≈ 978 ÷ H₀: 70 gives 14.0, 67.4 gives 14.5.
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Hubble and Lemaître
Georges Lemaître derived the expansion in 1927 and Edwin Hubble measured it in 1929, getting about 500 km/s/Mpc because his distances were too small.
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Not a speed
H₀ is a speed per distance, a rate: in SI it is about 2.3 × 10⁻¹⁸ per second.
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Background
About the Hubble constant
Galaxies recede from us faster the farther away they are; the Hubble constant H₀ is the rate: about 70 km/s for every megaparsec (3.26 million light-years) of distance.
Its inverse, the Hubble time, gives the age of a universe that expanded at a constant rate: about 14 billion years. Measurements disagree today: the cosmic microwave background gives 67.4, nearby supernovae 73 — the “Hubble tension”.