Redshift to fraction of light speed
Type a value in z to get it in c instantly.
0.09502c
That's 4.3× as distant as the Coma cluster, while the nearest quasar is 1.58× further. Light from it arrives about 10% longer in wavelength.
What it means
How far is that?
Distances use a simple Hubble law at 70 km/s per Mpc, which is only a good guide for small z. Beyond about z = 0.1 the real answer depends on the expansion history.
The math
How to convert z to c
Redshift is a stretch: 1 + z = observed ÷ emitted wavelength. Speed follows relativistically, v = c × ((1+z)² − 1) ÷ ((1+z)² + 1), and distance from v ÷ H₀ at 70 km/s per Mpc.
Example: 0.1 z = 0.0950226 c.
Every unit
Your redshift in every unit
Tables
z to c conversion table
| z | c |
|---|---|
| 0.001 z | 0.0009995 c |
| 0.01 z | 0.00995 c |
| 0.05 z | 0.0487515 c |
| 0.1 z | 0.0950226 c |
| 0.5 z | 0.384615 c |
| 1 z | 0.6 c |
| 2 z | 0.8 c |
| 3 z | 0.882353 c |
| 5 z | 0.945946 c |
| 7 z | 0.969231 c |
| 11 z | 0.986207 c |
c to z conversion table
| c | z |
|---|---|
| 0.001 c | 0.0010005 z |
| 0.00995 c | 0.01 z |
| 0.0488 c | 0.0500511 z |
| 0.095 c | 0.0999749 z |
| 0.385 c | 0.500677 z |
| 0.6 c | 1 z |
| 0.8 c | 2 z |
| 0.882 c | 2.99364 z |
| 0.946 c | 5.00309 z |
| 0.969 c | 6.9697 z |
| 0.986 c | 10.9104 z |
Quick answers
Quick answers
- How many c is 1 z?
- 1 z is 0.6 c.
- How many c is 10 z?
- 10 z is 0.983607 c.
- How many c is 0.1 z?
- 0.1 z is 0.0950226 c.
The units
About these units
Redshift (z)
The fractional stretch in wavelength, the number astronomers actually publish.
Fraction of light speed (c)
The same speed as a fraction of the speed of light.
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