# What means $h$ which appears following cosmological measured parameters?

For example, Big Bang Nucleossynthesis says that baryonic content in the Universe is around $$0.018 \leq \Omega_{b}h^{2} \leq 0.024$$. I know it is something related to measurement error but I do not where it comes from. Someone knows?

$$h$$ is a dimensionless version of the Hubble parameter $$H_0$$:
$$H_0=h\times 100\text{ km s}^{-1}\text{ Mpc}^{-1}$$
For example, $$h=0.7$$ means that the Hubble parameter is 70 kilometers per second per megaparsec.