Source: Earth weighs about 13,170,000,000,000,000,000,000,000 pounds (or 5,974,000,000,000,000,000,000,000 kilograms). Since Earth is too big to be placed on a scale, scientists use mathematics and the laws of gravity to figure out Earth's weight.
So, this seems to be a constant. But I guess it doesn't consider the things that are on the earth, the trees, buildings, people, animals, water etc...
So, are all the above mentioned things' weightmass is too small or negligible to be left off?