Hubble Law Calculator
Calculate galaxy recession velocities from distance using Hubble's law v = H₀d, with an adjustable Hubble constant (default 70 km/s/Mpc).
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
Default 70 km/s/Mpc (Planck/HST).
Formula
v = H₀ × d · H₀ ≈ 70 km/s/Mpc · d in Mpc, v in km/s
Hubble's law is valid in the low-redshift regime. For very distant galaxies, cosmological corrections (relativistic redshift, dark energy) are needed. H₀ is debated (Planck ~67.4, SH0ES ~73.0); adjust as needed.
This tool provides educational conversions of astronomical distances only. It is not a navigation, mission-planning, or ephemeris service. For professional or spacecraft work, use official IAU, NASA, or observatory data products.
About the Hubble Law Calculator
The Hubble’s law calculator relates the distance of a galaxy to the speed at which it is receding from us: v = H₀ × d, where H₀ is the Hubble constant. Measurements of H₀ currently range from about 67 to 73 km/s per megaparsec depending on the method — a disagreement known as the Hubble tension. The law applies to distant galaxies, where the expansion of the universe dominates over their own motion.
How to use it
- 1Set the Hubble constant (default 70 km/s/Mpc; Planck ~67.4, SH0ES ~73).
- 2Choose to solve for velocity (from distance) or distance (from velocity).
- 3Enter the known value and press Calculate.
Worked example
a galaxy 100 Mpc away recedes at v = 70 × 100 = 7,000 km/s. A galaxy receding at 14,000 km/s lies at about 200 Mpc (652 million light-years) for H₀ = 70.
How it works
Hubble\'s law
Edwin Hubble found that galaxies recede from us at a velocity proportional to their distance: v = H₀ × d, where H₀ is the Hubble constant (≈ 70 km/s/Mpc). This is the key evidence for the expanding universe.
The Hubble constant
Planck satellite data gives H₀ ≈ 67.4 km/s/Mpc, while the SH0ES team measures ≈ 73.0. This discrepancy — the Hubble tension — is one of cosmology\'s biggest open questions.
Who it is for
Cosmology students, astronomy enthusiasts, and anyone exploring the expanding universe.
Why it helps
Hubble's law is the observational cornerstone of modern cosmology — it shows the universe is expanding and lets you estimate galaxy distances from redshift.
Common use cases
- Estimating how fast a galaxy recedes from its distance
- Deriving a galaxy's distance from its recession velocity
- Teaching the expanding universe and cosmological redshift
- Exploring how H₀ affects distance estimates
Tips for better results
- Hubble's law is linear only at low redshift (z ≪ 1).
- The Hubble constant is debated; try 67.4 (Planck) and 73 (SH0ES) to see the range.
- 1 Mpc ≈ 3.26 million light-years.
- For high redshift, use a full cosmological model, not the linear law.
Common mistakes to avoid
- Applying the linear law at high redshift where cosmological effects matter.
- Mixing distance units (Mpc vs. light-years) without converting.
- Treating H₀ as exactly known — it carries real measurement uncertainty.
Frequently asked questions
A:Hubble's law states that a galaxy's recession velocity equals the Hubble constant times its distance: v = H₀d. It shows the universe is expanding.
A:The default is 70 km/s/Mpc, a common compromise. Planck gives ~67.4 and SH0ES ~73.0; you can adjust the value to explore the range.
A:It is linear only at low redshift (z ≪ 1). For very distant galaxies, relativistic and dark-energy corrections require a full cosmological model.
A:Yes. It runs in your browser on CalcWisee with no sign-up required.
Reviewed for accuracy · Last updated October 7, 2026
The astronomical unit is taken as exactly 149,597,870,700 metres per the IAU 2012 definition. Related light-time and light-year factors use the defined speed of light and the IAU Julian year where applicable.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
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References & sources
