Pregnancy Calorie Needs Calculator — By Trimester & Breastfeeding

How this calculator works

Your pre-pregnancy baseline is either the figure you enter or an estimate using the Mifflin-St Jeor equation for women (10 × weight kg + 6.25 × height cm − 5 × age − 161) × an activity factor. The Institute of Medicine's Dietary Reference Intakes then add:

• First trimester: no extra calories
• Second trimester: +340 kcal/day
• Third trimester: +452 kcal/day
• Breastfeeding, 0–6 months: +330 kcal/day (500 kcal for milk production, minus about 170 kcal supplied by postpartum weight loss)
• Breastfeeding, 7–12 months: +400 kcal/day

These figures are for a single baby and a healthy pre-pregnancy weight. Needs differ with twins, a higher or lower starting BMI, and activity level.

By Suhaib Hassan · Reviewed 28 September 2026 against the IOM Dietary Reference Intakes · How CalculatePilot verifies formulas →

A worked example

A 30-year-old, 5′5″ (165 cm), 140 lb (63.5 kg), lightly active: baseline = (635 + 1,031 − 150 − 161) × 1.375 ≈ 1,863 kcal. In the second trimester that's about 2,203 kcal a day, and about 2,315 in the third.

Quality matters alongside quantity

The extra energy needed is modest — "eating for two" overstates it. Clinical guidance focuses on nutrient-dense foods, a daily prenatal vitamin with at least 400 mcg of folic acid (recommended by the CDC before and during pregnancy), and the nutrient targets above. This is information, not medical advice — follow your care team's guidance, especially with twins, diabetes or other conditions.

Checking the number against real life

The extra calories are averages for one baby and a healthy starting weight, so treat the total as a starting point, not a prescription. A more useful check is how your weight is changing: compare it with the recommended range in the pregnancy weight gain calculator. If you are well above or below that range for several weeks, mention it to your care team rather than changing your calories on your own.

The printed numbers fit less well with severe nausea or vomiting in early pregnancy (it can be hard to eat enough), twins or more, a starting weight that is underweight or well above average, and teenagers who are still growing. Pregnancy is also not usually the time to cut calories to lose weight; if you are worried about gaining too much, ask your care team for a plan that fits you.

Sources

• Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005 (energy additions for pregnancy and lactation).
• Institute of Medicine / National Academies. Dietary Reference Intakes tables for vitamins, elements and macronutrients (pregnancy and lactation RDAs and AIs).
• CDC — Folic acid
• ACOG — Healthy Eating During Pregnancy (FAQ)

Frequently asked questions

Do I need extra calories in the first trimester?expand_more

For most women, no. The IOM adds no extra calories in the first trimester; extra needs start in the second trimester at about 340 kcal a day.

How many extra calories do I need with twins?expand_more

The IOM did not set energy additions for twins. Needs are higher than for one baby, so your care team or a registered dietitian can give you a personal target.

How many extra calories does breastfeeding use?expand_more

Making milk uses about 500 kcal a day in the first six months. Because some of that energy comes from body stores, the IOM adds about 330 kcal a day to your intake then, and about 400 kcal a day from 7 to 12 months.