Hi anirudh. The two common units for BGL are mmol/L and mg/dL, and the conversion factor between them is approx 18.
One mmol (milli-mole) of glucose weighs 180 mg (to nearest mg), so that means that 1 mmol/L is equal to 180 mg/L. One dL (deci-Litre) however is only one tenth of a Litre, so it follows that 1 mmol/L equates to 18 mg/dL.
So the upshot is that you simply multiply (or divide) by 18, depending on which way you are converting. For example:
10 mmol/L = 180 mg/dL
5 mmol/L = 90 mg/dL
and so on.