3.6 kilograms. 7.2 kg is 3.6 kg, which is our traditional unit of mass. 1 kg equals 500 g, so 7.2 kg equals 3600 g, and since 1 kg equals 1000 g, 3600 equals 3600 divided by 1000 equals 3.6kg.. Common weight conversion formulas are: 1kg = 1000g, 1g = 0.00 1kg, 1kg equals 500g, 1kg equals 1kg.