Pregnancy Iron Needs Calculator

About this calculator

Iron requirements roughly double during pregnancy because the body needs to expand maternal blood volume by up to 50%, supply the growing fetus and placenta, and build iron reserves for delivery blood loss — needs that rise sharply through the second and third trimesters as blood volume expansion accelerates. Dietary intake alone often falls short of the increased requirement, which is why iron-deficiency anemia is one of the most common nutritional deficiencies flagged in prenatal bloodwork.

Obstetricians and midwives use trimester-adjusted iron targets to decide when dietary iron is sufficient versus when a supplement is needed, and to set a supplemental dose that closes the specific gap between what a diet provides and what pregnancy actually requires at that stage — routine prenatal iron supplementation is standard practice in most guidelines specifically because deficiency is so common and consequential for both parent and baby.

This calculator takes your trimester and typical dietary iron intake and returns your estimated daily iron need along with the supplemental iron to add to close the gap.