Pregnancy Weight Gain Calculator
Monitor healthy week-by-week gestational weight trajectories stratified by pre-pregnancy Body Mass Index according to IOM and ACOG standards.
Pregnancy Weight Gain Calculator
Evidence-based gestational weight gain curves and trimester targets according to Institute of Medicine (IOM) and ACOG guidelines.
Expected cumulative gain
40-week IOM guideline
Category: Normal Weight
Gradual fetal & maternal tissue accrual
Institute of Medicine (IOM) & ACOG Clinical Guidance:
For a pre-pregnancy BMI of 22.8 (Normal Weight), the recommended total weight gain for a singleton pregnancy is 11.5–16 kg.
Target ranges reflect maternal blood volume expansion, placenta, amniotic fluid, and fetal tissue accrual. Weight gain during pregnancy is not simply fat accrual; it supports placental development, amniotic fluid, expanded maternal circulating blood volume (approx. 40–50%), breast tissue, and fetal growth. Always evaluate gestational progression in consultation with your obstetrician or midwife.
Clinical Screening Reference & Medical Notice
Calculations provided on HOW WEIGHT are based on published statistical standards (such as WHO, CDC, and peer-reviewed metabolic equations) and are intended for educational and general screening purposes only.
They do not directly measure body fat distribution or visceral adipose tissue, nor do they replace personalized clinical diagnostic evaluation by a licensed healthcare provider. Learn more about our clinical methodology & disclaimers →
The Institute of Medicine (IOM) & ACOG Clinical Guidelines
In 2009, the Institute of Medicine (now the National Academy of Medicine) together with the National Research Council released re-examined evidence-based gestational weight gain recommendations, subsequently endorsed by the American College of Obstetricians and Gynecologists (ACOG). Rather than applying a single uniform target for all expectant mothers, these clinical standards tailor recommended weight gains to pre-pregnancy BMI to minimize risks of gestational diabetes, preeclampsia, cesarean delivery, macrosomia, and preterm birth.
| Pre-Pregnancy BMI | Category | Total Recommended Gain (kg / lbs) | 2nd & 3rd Trimester Rate |
|---|---|---|---|
| < 18.5 | Underweight | 12.5 – 18.0 kg (28 – 40 lbs) | 0.44 – 0.58 kg/wk (~1.0–1.3 lb/wk) |
| 18.5 – 24.9 | Normal Weight | 11.5 – 16.0 kg (25 – 35 lbs) | 0.35 – 0.50 kg/wk (~0.8–1.0 lb/wk) |
| 25.0 – 29.9 | Overweight | 7.0 – 11.5 kg (15 – 25 lbs) | 0.23 – 0.33 kg/wk (~0.5–0.7 lb/wk) |
| ≥ 30.0 | Obesity | 5.0 – 9.0 kg (11 – 20 lbs) | 0.17 – 0.27 kg/wk (~0.4–0.6 lb/wk) |
Worked Gestational Tracking Example
Consider a woman with a pre-pregnancy weight of 62.0 kg (136.7 lbs) at a height of 165 cm (5 ft 5 in):
- Pre-Pregnancy BMI: 62 ÷ (1.65 × 1.65) = 22.8 (Normal Weight category).
- Total 40-Week Recommended Target: 11.5 to 16.0 kg (25 to 35 lbs).
- Expected Gain by Week 20 (Mid-Pregnancy): 1st trimester (~1.2 kg) + 7 weeks of 2nd trimester (~0.42 kg/wk) = approx. 4.1 to 4.8 kg (9.0 to 10.6 lbs) cumulative gain.
Frequently Asked Questions
How much weight should I gain during pregnancy?
The Institute of Medicine (IOM) and American College of Obstetricians and Gynecologists (ACOG) recommend total gestational weight gain based on your pre-pregnancy BMI: Normal weight (BMI 18.5–24.9): 11.5 to 16.0 kg (25–35 lbs); Underweight (BMI < 18.5): 12.5 to 18.0 kg (28–40 lbs); Overweight (BMI 25.0–29.9): 7.0 to 11.5 kg (15–25 lbs); and Obesity (BMI ≥ 30.0): 5.0 to 9.0 kg (11–20 lbs).
How much weight should I expect to gain in the first trimester?
During the first trimester (weeks 1 to 13), fetal size is minimal. Total expected weight gain is generally between 0.5 and 2.0 kg (1.1 to 4.4 lbs) for the entire 13-week period. Some women experience slight temporary weight loss during early weeks due to morning sickness (nausea and vomiting of pregnancy).
Where does the pregnancy weight gain actually go?
Gestational weight gain is distributed across vital biological compartments: the baby (~3.5 kg / 7.5 lbs), placenta (~0.7 kg / 1.5 lbs), amniotic fluid (~1.0 kg / 2 lbs), expanded uterine muscle (~1.0 kg / 2 lbs), maternal blood volume expansion (~1.5 to 2.0 kg / 3–4 lbs), extracellular breast and bodily fluids (~2.0 kg / 4 lbs), and maternal maternal fat/nutrient stores (~3.0 kg / 7 lbs) for lactation.
Should you ever diet or try to lose weight during pregnancy?
No. Intentional caloric restriction or weight loss diets are strictly contraindicated during pregnancy because they can lead to maternal ketosis, intrauterine growth restriction (IUGR), and impaired fetal neurodevelopment. Nutritional focus should remain on nutrient-dense foods, adequate hydration, and obstetrician-supervised monitoring.
What are the recommended weight gain ranges for twin pregnancies?
For twin gestations, the IOM recommends higher total gain to support two developing fetuses: 16.8 to 24.5 kg (37–54 lbs) for women with normal pre-pregnancy BMIs, 14.1 to 22.7 kg (31–50 lbs) for overweight women, and 11.3 to 19.1 kg (25–42 lbs) for women with obesity.