Breastfeeding Calorie Calculator

The calculator works in two steps. First it estimates the calories you burn on a normal day: your basal metabolic rate (BMR) from the Mifflin-St Jeor equation for women (10 × weight in kg + 6.25 × height in cm − 5 × age − 161), multiplied by an activity factor from 1.2 to 1.9. Then it adds the energy that making milk takes, using the lactation terms in the National Academies' 2023 Dietary Reference Intakes for Energy (NASEM). There, a breastfeeding woman's estimated energy requirement is her usual energy expenditure plus the energy cost of milk production, minus any energy drawn from body tissue.

NASEM adds its figures to current energy expenditure, which is what your inputs describe. The 2020–2025 Dietary Guidelines for Americans and the CDC state theirs relative to what you ate before pregnancy, so the result panel shows them alongside rather than mixing the two. The newer 2025–2030 Dietary Guidelines say lactation increases energy needs but give no number.

Why the Extra Calories Change by Month

In the first 6 months of exclusive breastfeeding, NASEM puts the energy cost of milk production at 540 calories a day. It then subtracts 140 calories a day, the average amount drawn from fat stored in pregnancy, for a net of 400. The Dietary Guidelines follow the same logic with older figures: 500 calories for milk minus 170 for postpartum weight loss, or +330. The two together explain the CDC's range of an additional 330 to 400 calories a day for well-nourished breastfeeding mothers.

From 7 to 12 months most babies also eat solid foods, so milk output falls. NASEM uses 380 calories a day for milk output of about 570 g a day, and assumes your weight is stable by then; the Dietary Guidelines use +400. In the second year, NASEM describes the cost as variable, depending on how much your child nurses, so the calculator shows a range.

Why Your Feeding Pattern Matters

The CDC notes that the extra calories you need also depend on your age, body mass index, activity level and whether you breastfeed exclusively or combine breast milk with formula. No guideline publishes a figure for combined feeding, so the calculator shows a range from your maintenance calories up to the breast-milk-only figure: the less milk you make, the closer you are to the low end. There is no guideline figure for nursing twins either. The Dietary Guidelines list multiple pregnancies among the factors that can change calorie needs, so ask your provider.

The Institute of Medicine's report Nutrition During Lactation (1991) found that the weight loss lactating women usually experience has no apparent harmful effect on milk production, with an average loss of 0.5 to 1 kg (about 1 to 2 lb) a month after the first month. For overweight women, a loss of up to 2 kg (about 4.5 lb) a month is unlikely to reduce milk volume, though they should watch for signs that the baby is still hungry. Losing faster than that after the first month is not advisable.

The main trial is small. In Lovelady and colleagues' 2000 study in the New England Journal of Medicine, 40 overweight, exclusively breastfeeding women were assigned at 4 weeks postpartum either to eat 500 calories a day less and exercise 45 minutes on 4 days a week, or to carry on as usual. Over 10 weeks the diet-and-exercise group lost 4.8 kg against 0.8 kg, and their babies grew just as well. That is where the calculator's gradual-loss target comes from.

Keep a floor under it. The same IOM report encourages at least 1,800 calories a day while breastfeeding and says intakes below 1,500 are not recommended at any time during lactation. Our guide to minimum calorie intake covers calorie floors for adults in general. If you want to see your non-breastfeeding baseline, the TDEE calculator gives it on its own.

• Iodine, choline and seafood. The CDC gives 290 mcg of iodine and 550 mg of choline a day during lactation and lists seafood low in mercury but rich in DHA among the key food sources. The Dietary Guidelines advise at least 8 and up to 12 ounces of a variety of seafood a week, from choices lower in methylmercury. See our list of iodine-rich foods.
• Protein and calcium. The Dietary Reference Intakes set protein at 71 g a day and calcium at 1,000 mg a day for breastfeeding women aged 19–50. The protein intake calculator and our guide to calcium-rich foods help you get there.
• Vitamin D for your baby. According to the CDC, the American Academy of Pediatrics recommends that breastfed and partially breastfed infants get 400 IU of vitamin D a day, starting in the first few days of life.
• Vitamin B12 on a plant-based diet. The CDC warns that breastfed infants of women who eat no animal products may get very little vitamin B12. Ask your provider about supplements.
• Fluids. The adequate intake of total water during lactation is 3.8 liters a day, counting food as well as drinks. The ODPHP suggests a glass of water or another unsweetened drink every time you breastfeed; the IOM advises drinking to satisfy thirst, and no more is needed.

Caffeine and Alcohol

• Caffeine. The CDC calls about 300 mg a day or less, about 2 to 3 cups of coffee, a low to moderate amount. Irritability, poor sleep, fussiness and jitteriness have been reported in babies whose mothers had very high intakes, about 10 cups of coffee or more a day.
• Alcohol. The CDC says not drinking is the safest option. Up to one drink a day is not known to be harmful to the infant, and to be safest you can wait at least 2 hours after a single drink before nursing.

These numbers are population estimates. Your doctor or a lactation consultant can tailor them, and you should talk to them if your milk supply drops or your baby's weight gain slows.