Hubble's Law Calculator

What Is Hubble's Law?

Hubble's law states that distant galaxies recede from us at a speed proportional to their distance. It is one of the main pieces of evidence for cosmic expansion and underpins modern cosmological distance scales.

Hubble's Law Formula

$$v = H_0 \times d$$

$v$ is recession velocity, $d$ is distance, and $H_0$ is the Hubble constant. A commonly used value is $H_0 \approx 70\,\text{km/s/Mpc}$, though precise measurements from CMB and supernovae surveys cluster around 67 to 74 km/s/Mpc.

Units in Cosmology

Recession velocity is often in km/s. Distance is commonly in megaparsecs (Mpc) or million light-years. The Hubble constant can also be expressed in inverse seconds (s⁻¹) for unit consistency in physics calculations.

Explore related tools: Redshift Calculator and Age on Other Planets Calculator.

Frequently Asked Questions

What value of H₀ should I use?

70 km/s/Mpc is a good classroom estimate. Research values differ slightly depending on measurement method. Enter the value your problem specifies.

Does Hubble's law work at all distances?

It is an approximation for relatively nearby galaxies. At very large distances, relativistic effects and the changing expansion rate matter.

What is a megaparsec?

One megaparsec (Mpc) is about 3.26 million light-years. It is a standard distance unit in extragalactic astronomy.

Can I solve for distance instead of velocity?

Yes. Rearrange to $d = v / H_0$. Select "Distance" in the solve-for dropdown.

Is recession velocity the same as redshift?

Related but not identical. For small velocities, redshift $z \approx v/c$. At high speeds, use relativistic redshift formulas.

Report

What Is Hubble's Law?

Hubble's Law Formula

Units in Cosmology

Frequently Asked Questions

Related Tools

Recent Visits