Which is exactly why I would advise OP against trying to convert their teaspoons into grams. Unless they're very careful, they're bound to get inaccurate result

Which is exactly why I would advise OP against trying to convert their teaspoons into grams. Unless they're very careful, they're bound to get inaccurate results. As it happens, baking soda has a density of 2.2g/cm^3. But the powdered form contains lots of air between the granules, so the actual density comes down to somewhere just above the density of water. Using 3g instead of 2.5g in a recipe, though, will yield very different results.