WebMD reports that ferrous sulfate, which contains 20% elemental iron, is the most popular iron supplement. There are about 65 mg of elemental iron in a 325 mg ferrous sulfate tablet.

Nature Made boasts 65 mg of iron per capsule — that’s 361% of the DV for iron, or the equivalent of 325 mg of ferrous sulfate. ... These chewable tablets have a sweet cherry flavor but are ...