What is Hubble's Law?

Hubble's Law states that the recession velocity of a galaxy is directly proportional to its distance from us. The proportionality constant is the Hubble constant (H0), typically expressed in km/s/Mpc. This calculator uses the formula v = H0 × d to estimate the velocity.

What units should I use for distance?

Distance should be entered in megaparsecs (Mpc). One parsec is about 3.26 light-years, and a megaparsec is one million parsecs. The Hubble constant is in km/s/Mpc, so using Mpc for distance gives velocity in km/s.

What is a typical value for the Hubble constant?

Current estimates range from about 67 to 74 km/s/Mpc, depending on the measurement method. For example, Planck satellite data suggest around 67.4 km/s/Mpc, while some distance ladder methods give about 73 km/s/Mpc. You can use any value you like.

Physik

Sofort, privat und kostenlos

Hubble's Law Calculator.

Estimate recession velocity from the Hubble constant and distance.

Berechnung auf dem GerätKeine Anmeldung

Werte eingeben

Ergebnisse werden während der Eingabe aktualisiert.

02 / ANTWORT

Hubble constant

Distance

Recession velocity

700

Educational SI models with assumptions stated in each description; verify engineering decisions independently.

Use Cases

Astronomy Education

Helps students and enthusiasts understand the relationship between distance and recession velocity in an expanding universe.

Example: Calculate the velocity of a galaxy at 100 Mpc with H0 = 70 km/s/Mpc.

Research Data Analysis

Quickly estimate velocities for given distances when analyzing galaxy survey data or testing cosmological models.

Example: Estimate velocities for a list of galaxies with known distances.

Frequently Asked Questions

What is Hubble's Law?: Hubble's Law states that the recession velocity of a galaxy is directly proportional to its distance from us. The proportionality constant is the Hubble constant (H0), typically expressed in km/s/Mpc. This calculator uses the formula v = H0 × d to estimate the velocity.
What units should I use for distance?: Distance should be entered in megaparsecs (Mpc). One parsec is about 3.26 light-years, and a megaparsec is one million parsecs. The Hubble constant is in km/s/Mpc, so using Mpc for distance gives velocity in km/s.
What is a typical value for the Hubble constant?: Current estimates range from about 67 to 74 km/s/Mpc, depending on the measurement method. For example, Planck satellite data suggest around 67.4 km/s/Mpc, while some distance ladder methods give about 73 km/s/Mpc. You can use any value you like.

Tips & Common Mistakes

Tips

Ensure the Hubble constant is in km/s/Mpc and distance in Mpc to get velocity in km/s.
Use consistent units: if you have distance in light-years, convert to Mpc first (1 Mpc ≈ 3.26 million light-years).
Remember that Hubble's Law is an approximation valid for large distances where peculiar velocities are small.
For accurate cosmological calculations, consider using the exact formula that accounts for relativistic effects, but this simple estimate is fine for most educational purposes.

Common Mistakes to Avoid

Forgetting to convert distance to Mpc when using a Hubble constant in km/s/Mpc.
Using the Hubble constant in different units (e.g., km/s per light-year) without conversion.
Assuming the law applies to nearby galaxies where gravitational interactions dominate over cosmic expansion.

Last updated: August 13, 2026