Remember that there are 1000 grams in a kilogram.

So, given a mass in kg, we multiply by 1000 to convert this to g.  

Any additional grams must be added on.

Examples

6.2 kg = 6.2 x 1000 = 6200 g

6.25 kg = 6.25 x 1000 = 6250 g

6.025 kg = 6.025 x 1000 = 6025 g

6 kg 20 g = 6 x 1000 + 20 = 6020 g