Pregnancy Weight Gain Chart by Week

How much should you gain each week of pregnancy? The Institute of Medicine (IOM) sets recommended ranges based on your pre-pregnancy BMI: most women with a normal BMI (18.5–24.9) should gain 25–35 lbs (11.5–16 kg) in total, with about 0.8–1.0 lbs (0.35–0.5 kg) per week during the second and third trimesters. First-trimester gain is modest — only 1–4 lbs (0.5–2 kg) total for most women. This guide walks you through the full week-by-week pregnancy weight gain chart so you can see where you should be at weeks 14, 20, 28, 36, and 40 — and what to do if you fall outside the range.

How much weight should I gain during pregnancy?

The IOM recommends a total pregnancy weight gain range based on your pre-pregnancy BMI. Women who start pregnancy underweight should gain the most, while those who start with obesity should gain the least. Here are the official ranges:

These are ranges, not single targets. The IOM deliberately frames its guidance as ranges because healthy pregnancies vary widely — two women in the same BMI category can gain quite different amounts and both have healthy outcomes. Your provider personalizes the range based on your health history, so treat this chart as a starting point, not a rulebook.

How much weight should I gain in the first trimester?

Very little — for most women, total first-trimester gain (weeks 1–13) is only about 1–4 lbs (0.5–2 kg), and the IOM's calculations assume roughly 1–4.4 lbs. Morning sickness can even cause slight weight loss early on, which is usually fine as long as you stay hydrated. The chart below reflects this slow start: cumulative gain stays nearly flat through week 13, then climbs steadily from week 14 onward. If you are unsure where you are in your pregnancy, use our pregnancy week calculator to find your current gestational week, or check your estimated due date first.

What does the week-by-week pregnancy weight gain chart look like?

For a woman with a normal pre-pregnancy BMI (18.5–24.9), cumulative weight gain follows this approximate pattern. Figures are rounded IOM-consistent ranges; use them as a trend guide rather than an exact prescription.

The key pattern is simple: almost flat for the first 13 weeks, then roughly a pound a week from week 14 to week 40. If you weigh yourself weekly, plot your progress against this trend rather than fixating on any single number.

How does the chart change if I am underweight or overweight?

The shape of the chart stays the same — slow first trimester, then steady weekly gain — but the slope steepens or flattens with your starting BMI. Use the IOM weekly rates from the summary table above and apply them from week 14:

• Underweight (BMI below 18.5). Expect about 1.0–1.3 lbs (0.45–0.6 kg) per week after week 13, toward a 28–40 lbs (12.5–18 kg) total. By week 40 you may be near 35–40 lbs of cumulative gain at the upper end.
• Normal weight (BMI 18.5–24.9). The standard curve above: about 0.8–1.0 lbs (0.35–0.5 kg) per week, 25–35 lbs (11.5–16 kg) total.
• Overweight (BMI 25.0–29.9). About 0.5–0.7 lbs (0.2–0.3 kg) per week, 15–25 lbs (7–11.5 kg) total. At week 28 you might expect roughly 9–14 lbs of cumulative gain.
• Obese (BMI 30 or above). About 0.4–0.6 lbs (0.2–0.3 kg) per week, 11–20 lbs (5–9 kg) total. The chart flattens significantly — some weeks may show no gain at all, which can be normal at this starting BMI.

The pregnancy weight gain calculator applies the correct weekly rate for your category automatically, so you can track your personal curve week by week instead of doing the arithmetic yourself.

Where does all the weight actually go?

It helps to know that most of the 25–35 lbs is not fat. Roughly 7–8 lbs is the baby, with the rest distributed across the placenta, amniotic fluid, increased blood volume, larger breasts and uterus, and extra fluid and fat stores that support breastfeeding later. Because so many components are involved, week-to-week fluctuations of 1–2 lbs from water and meals are normal — what matters is the trend over several weeks, not any single weigh-in.

What about weight gain with twins or triplets?

The charts above apply to singleton pregnancies. The IOM gives separate, higher recommended ranges for twins and higher-order multiples, and these are typically set and monitored by your provider based on how the pregnancy progresses. Rather than following the standard chart, discuss your target with your OB-GYN or midwife early in pregnancy — they will usually schedule closer monitoring and may use specialized growth tracking. You can still use the pregnancy weight gain calculator to record your weekly measurements for those check-ins.

What if I am gaining too much or too little?

First, do not panic over one reading — weigh at the same time of day, on the same scale, and look at the two-to-three-week trend. If you are consistently above your range, your provider may suggest reviewing portion sizes and adding gentle activity like walking, while keeping nutrient quality high. If you are consistently below your range, they may recommend adding calorie-dense but nutritious foods such as nuts, dairy, and whole grains. Sudden, sharp jumps — especially with swelling in the face or hands — warrant a prompt call to your provider, as they can signal conditions like preeclampsia. Never diet for weight loss during pregnancy without explicit medical direction.

For a broader picture of maternal and child health tools, browse our women and kids health calculators hub.

Pregnancy Weight Gain FAQs

Written by the Live Fitness Check editorial team · Reviewed against our calculator methodology · Last updated October 2026

Disclaimer: This guide is for educational purposes only and is not medical advice. Weight-gain targets vary by individual pregnancy — always follow the guidance of your OB-GYN or midwife, especially with multiples or medical conditions.