Literally weighing the Earth would be next to impossible. There planet is suspended in space and cannot be put on a scale and weighed. However, scientists made an assumption on how the Earth weighed by estimating the weight of each of its parts: the crust, the mantle, and the core.
They came up with this figure: 6.6 sextillion tons! That's two 6's followed by twenty zero's, or 6,600,000,000,000,000,000,000 tons!
And for your information, the earth’s weight continues to increase by 100,000 pounds each year. This is due to the dust and meteoric material falling from the sky, from the residue of burning fuel, and from salt from the ocean spray!