How many grams will be used in a print
You can not tell this by looking at the STL file alone, because how much material will be used depends on the print settings (obviously, printing at 100% infill will consume much more material than 10%).

The best way to check the material usage is to load the model into a slicer and slice it using your preferred settings. Most slicers will report the projected material usage, often in grams but sometimes in meters of filament (but the two figures are easily converted between each other if you know the density and diameter of your material).

Here is an example in the Cura slicer:



Simplify3D (after you click "prepare to print!") also shows you the projected print time and material usage and even the cost of the material (if you have previously entered the material cost per kilogram):