The conversion uses a density of 1.000 g/mL for water. Different forms of the same ingredient (e.g. sifted vs. packed flour) can shift the result by up to 30%.
Milligrams measure mass; tablespoons measure volume. The link between them is always the ingredient density, which is why two tablespoons of flour weigh far less than two tablespoons of honey.
Next stepFor baking, weigh your ingredients in grams on a kitchen scale for greater accuracy than volume scooping.