Oxygen is sp³ hybridised in H₂O molecule. Two hybrid orbitals are occupied by lone pairs and two are used in sigma bonding with hydrogen atoms. Now, the expected tetrahedral angle is 109.5° but the actual bond angle observed is 104.5°. This because from VSEPR theory, we know that lone pair-lone pair repulsions are greater than bond pair-bond pair repulsions and the same situation we observe here. As a result, bond angle in water is 104.5°.