In this paper, we derived two Ostrowski--Grüss type inequalities on time scales involving a combination of $\Delta$-integral means. One of the inequalities is sharp. We also obtained 2-dimensional Ostrowski type inequality involving a combination of $\Delta$-integral means. Our results extend some known results in the literature. Furthermore, we apply our results to the continuous, discrete and quantum calculus to obtain some interesting inequalities in these directions.