A dipole moment is a quantity that describes two opposite charges separated by a distance and hence its a vector quantity.

Dipole moments tell us, on average, where the electrons in a molecule are and they can also tell us the shape of molecules.

**Formula to calculate dipole moment.**

**Example:**

Calculate the dipole moment of a water molecule.

Since the bond moment of the O-H bond is -1.5 Debyes.

The H−O−H bond angle of water is pretty much 104.5 degrees. Then we divide 104.5 by 2 to get 52.25 degrees for each side, then imagine two right angles.

With that, and the fact that cosθ=cos(−θ).

Therefore, our left contribution will be;

**= 1.5 x cos ( -52.25 )**

**= 0.918**

And our right contribution will be the same as the left contribution.

**= 0.918**

Finally, we sum them up.

** = 0.918 + 0.918**

**= 1.836 D**