Hubble's Law Distance Calculator
Hubble's law links how fast a galaxy is receding to how far away it is: the faster it moves away, the more distant it is. This calculator turns a measured recession velocity into a distance in megaparsecs and light years, using a Hubble constant you can set yourself. Because the measured value of the Hubble constant differs between methods, keeping it editable lets you work with whichever figure your analysis assumes and see directly how the distance estimate depends on it.
Hubble's law formula
distance (Mpc) = recession velocity (km/s) / Hubble constant (km/s per Mpc)
distance (million light years) = distance (Mpc) * 3.26156
One megaparsec equals about 3.26156 million light years. The Hubble constant is editable because its measured value is method dependent.
Worked example
A galaxy receding at 7,000 km/s with a Hubble constant of 70 km/s per Mpc lies at 7,000 / 70 = 100.00 megaparsecs, which is about 326.16 million light years away.
Hubble's law: frequently asked questions
What is Hubble's law?
Hubble's law states that distant galaxies recede from us at a velocity proportional to their distance: velocity equals the Hubble constant times distance. The proportionality reflects the expansion of the universe, where more distant galaxies move away faster simply because more space lies between us and them.
What value should I use for the Hubble constant?
The Hubble constant is the subject of active research, with different methods giving values broadly in the range of about 67 to 74 kilometres per second per megaparsec. Because there is no single settled figure, this calculator makes the Hubble constant an editable input so you can use whichever value your work assumes and see how the distance changes.
When does Hubble's law stop being accurate?
Hubble's law is a good approximation for relatively nearby galaxies whose recession is dominated by cosmic expansion. For very distant, high-redshift objects, the simple linear law breaks down and a full cosmological model is needed, and for nearby galaxies, local gravitational motions (peculiar velocities) can dominate over the expansion signal.
Sources
- Hubble's law and the expanding universe: NASA NASA Science: The Expanding Universe. The Hubble constant is an editable input because its measured value is method dependent.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.