Pregnancy Calorie Calculator
Calculate your daily calorie needs for each trimester based on IOM guidelines and the Mifflin-St Jeor equation
Your Pregnancy Calorie Results
Understanding Calorie Needs During Pregnancy
Pregnancy increases your body's energy demands to support the growth and development of your baby, placenta, uterus, and increased blood volume. However, the popular notion of "eating for two" is misleading. The actual additional calorie requirements are far more modest than most people assume. According to the 2009 Institute of Medicine (IOM) guidelines, which remain the clinical standard used by obstetricians and dietitians worldwide, no extra calories are needed during the first trimester, an additional 340 calories per day are recommended during the second trimester, and an additional 450 calories per day during the third trimester. These recommendations are based on the Estimated Energy Requirement (EER) equations and account for the energy cost of tissue deposition during pregnancy.
The Mifflin-St Jeor equation is widely considered the most accurate formula for estimating Basal Metabolic Rate (BMR) in the general adult population. It calculates the number of calories your body burns at complete rest to maintain vital functions such as breathing, circulation, and cell production. Your Total Daily Energy Expenditure (TDEE) is then determined by multiplying your BMR by an activity factor that reflects your typical physical activity level. During pregnancy, the trimester-specific calorie additions are applied on top of this TDEE to account for the metabolic demands of fetal growth, placental development, and maternal tissue expansion.
Protein requirements increase significantly during pregnancy, particularly in the second and third trimesters when the baby's growth accelerates. The recommended dietary allowance (RDA) for protein during pregnancy is 1.1 grams per kilogram of body weight per day, compared to 0.8 grams for non-pregnant adults. This translates to roughly 25 additional grams of protein daily. High-quality protein sources include lean meats, poultry, fish (choosing low-mercury varieties), eggs, dairy products, legumes, nuts, and seeds. Adequate protein intake supports the development of fetal organs, the expansion of maternal blood volume, and the growth of breast and uterine tissue.
It is important to recognize that calorie needs during pregnancy are not one-size-fits-all. Women who enter pregnancy with obesity (BMI 30 or above) may not need any caloric increase or may benefit from a modest reduction in intake under medical supervision, as excessive calorie consumption increases the risk of gestational diabetes, preeclampsia, and macrosomia. Conversely, underweight women may need greater caloric increases to support healthy weight gain. Age, activity level, and the number of fetuses also influence individual needs. This calculator provides a research-based starting point, but your healthcare provider should guide your personalized nutrition plan throughout pregnancy.
How to Use This Pregnancy Calorie Calculator
- Select your preferred unit system (Metric or Imperial) using the toggle at the top of the form. All weight and height fields will adjust accordingly.
- Enter your pre-pregnancy weight. This is the weight you were at before becoming pregnant or at your first prenatal visit. It is used to calculate your baseline metabolic rate.
- Enter your height and age. The calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR) from these values.
- Select your current trimester from the dropdown. The calculator adds the IOM-recommended calories specific to your trimester: zero for the first, 340 for the second, and 450 for the third.
- Choose your activity level to determine your Total Daily Energy Expenditure (TDEE). Click "Calculate Calorie Needs" to see your personalized results, including BMR, TDEE, trimester addition, total daily target, and a recommended macro breakdown with protein emphasis.
Frequently Asked Questions
How many extra calories do I need during pregnancy?
According to the 2009 IOM guidelines, you need no additional calories during the first trimester (weeks 1 through 13), an extra 340 calories per day during the second trimester (weeks 14 through 27), and an extra 450 calories per day during the third trimester (weeks 28 through 40). These additions are on top of your normal daily energy expenditure. The modest first-trimester requirement surprises many women, but the embryo is very small during this period and most caloric demand comes later when the fetus grows rapidly.
What formula does this calculator use?
This calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR). The formula for women is: BMR = (10 x weight in kg) + (6.25 x height in cm) - (5 x age in years) - 161. Your BMR is then multiplied by an activity factor to determine your Total Daily Energy Expenditure (TDEE). Finally, the IOM 2009 trimester-specific calorie addition (0, 340, or 450 kcal/day) is added to calculate your pregnancy calorie target.
How much protein do I need during pregnancy?
The recommended dietary allowance for protein during pregnancy is 1.1 grams per kilogram of body weight per day, which is about 25 grams more than the non-pregnant recommendation. For a 65 kg woman, this means roughly 71 grams of protein daily. This calculator uses an enhanced protein split of approximately 25 to 30 percent of total calories, which aligns with current clinical guidance emphasizing higher protein intake during pregnancy to support fetal tissue development, placental growth, and maternal blood volume expansion.
Should I eat more if I am carrying twins?
Yes. Women carrying twins or multiples have greater caloric needs than those with singleton pregnancies. The IOM suggests that women carrying twins need approximately 300 to 500 additional calories per day beyond what a singleton pregnancy requires. This calculator is designed for singleton pregnancies. If you are expecting multiples, consult your healthcare provider or a registered dietitian for personalized calorie and nutrition targets.
Do I need extra calories if I am overweight or obese?
Women who enter pregnancy with a BMI of 30 or above may not need additional calories or may need a slight reduction under medical supervision. The IOM guidelines still recommend some weight gain for obese women (5 to 9 kg total), but excessive caloric intake increases the risk of gestational diabetes, preeclampsia, and delivery complications. Your healthcare provider can help you determine an appropriate calorie target based on your individual health profile and pregnancy progression.
Is it safe to exercise during pregnancy and does it affect calorie needs?
For most pregnancies, moderate exercise is safe and recommended. The American College of Obstetricians and Gynecologists advises at least 150 minutes of moderate-intensity aerobic activity per week during pregnancy. Exercise does increase your calorie needs, which is why this calculator includes an activity level selector. If you maintain an active lifestyle during pregnancy, selecting the appropriate activity level will account for those additional energy demands. Always get clearance from your healthcare provider before starting or continuing an exercise program during pregnancy.
When should I start eating more during pregnancy?
The IOM guidelines indicate that no additional calories are needed during the first trimester. The extra calorie intake should begin at the start of the second trimester (around week 14) with an additional 340 calories per day, increasing to 450 extra calories per day at the start of the third trimester (around week 28). However, these are averages, and some women may need to start earlier if they are underweight or experiencing significant morning sickness that limits food intake. Your healthcare provider can advise you on the best timing based on your individual circumstances.
