The tetrahedral crystal field splitting is only....... of the octahedral splitting.

Crystal Field Stabilization Energy (CFSE) is the additional stabilization gained by the splitting of the d-orbitals. The tetrahedral CFSE is expressed as Δ_t and octahedral CFSE is expressed as Δ_o.

In crystal field theory, it can be shown that the amount of splitting in a tetrahedral field is much smaller than in an octahedral field. In general,

${\mathrm{\Delta }}_{\mathrm{t}}=\frac{4}{9}{\mathrm{\Delta }}_0$