How much weight should I gain each week in pregnancy?

Most weight gain happens in the second and third trimesters. In the first trimester, gaining about 0.5-2 kg (1-4.5 lb) total is normal. After that, women of normal weight typically gain about 0.4-0.5 kg (around 1 lb) per week, overweight women about 0.2-0.3 kg per week, and women with obesity about 0.2 kg per week.

Where does pregnancy weight gain go?

Only a portion is the baby. At term a baby weighs about 3-3.5 kg, the placenta about 0.7 kg, and amniotic fluid about 0.8 kg. The rest is increased blood volume (about 1.2-1.5 kg), larger uterus and breasts, extra body fluid and fat stores that your body builds up to support breastfeeding.

Is it bad to gain too much or too little weight in pregnancy?

Gaining too much can raise the risk of gestational diabetes, high blood pressure, a larger baby and a harder delivery, and makes weight harder to lose afterwards. Gaining too little can increase the risk of a low-birth-weight or premature baby. Staying within your recommended range is best, but always follow the advice of your own doctor or midwife.

How much weight should I gain if I am expecting twins?

Twin pregnancies need more weight gain. The Institute of Medicine recommends 16.8-24.5 kg (37-54 lb) for women of normal weight, 14.1-22.7 kg (31-50 lb) for overweight women, and 11.3-19.1 kg (25-42 lb) for women with obesity. There is not enough data for a firm underweight twin guideline, so discuss your target with your doctor.

🤰 Pregnancy

Pregnancy Weight Gain Calculator 2026

See how much weight you should gain during pregnancy based on your pre-pregnancy BMI and how far along you are. Built on the official Institute of Medicine (IOM) guidelines — works in kg or lb and supports twin pregnancies.

Units

Height (cm)

Your height — used to work out your pre-pregnancy BMI

Pre-pregnancy weight (kg)

Weight before you got pregnant

Current weight (kg)

Your weight today (optional)

How many weeks pregnant are you?

Current week of pregnancy (0-42)

I'm expecting twins

Tick this if you're carrying twins — the healthy range is higher.

Recommended Total Weight Gain

Based on your pre-pregnancy BMI

⚖️ Pre-pregnancy BMI -- --

🎯 Recommended total gain --

📅 Recommended by now (week --) --

📈 You've gained so far --

✅ Status --

🍼 Weekly gain (2nd-3rd tri) --

📋 Official IOM Weight-Gain Guidelines

Single baby — total recommended gain across the whole pregnancy
Pre-pregnancy BMI	Category	Total gain
Below 18.5	Underweight	12.5–18 kg (28–40 lb)
18.5 – 24.9	Normal weight	11.5–16 kg (25–35 lb)
25.0 – 29.9	Overweight	7–11.5 kg (15–25 lb)
30.0 and above	Obese	5–9 kg (11–20 lb)

Twins — total recommended gain
Pre-pregnancy BMI	Category	Total gain
18.5 – 24.9	Normal weight	16.8–24.5 kg (37–54 lb)
25.0 – 29.9	Overweight	14.1–22.7 kg (31–50 lb)
30.0 and above	Obese	11.3–19.1 kg (25–42 lb)

Source: Institute of Medicine (now the National Academy of Medicine), Weight Gain During Pregnancy: Reexamining the Guidelines (2009). There isn't enough data for a firm underweight-twin range, so check with your doctor.

🍼 Where Does the Weight Actually Go?

Only a small part of pregnancy weight is the baby. Here's a rough breakdown for an average term pregnancy with a total gain of about 12.5 kg (27.5 lb):

👶 Baby~3.4 kg (7.5 lb)

🩸 Increased blood volume~1.4 kg (3 lb)

💧 Body fluids~1.4 kg (3 lb)

🤰 Larger uterus~0.9 kg (2 lb)

🫗 Amniotic fluid~0.8 kg (1.8 lb)

🧫 Placenta~0.7 kg (1.5 lb)

🤱 Larger breasts~0.9 kg (2 lb)

🛡️ Fat & nutrient stores~3.5 kg (7.7 lb)

🥗 Tips for Healthy, Steady Gain

🍽️ You don't need to "eat for two"

In the first trimester you usually need no extra calories. In the second trimester aim for about 340 extra calories a day, and in the third about 450 extra — roughly a healthy snack, not a second meal.

🥦 Focus on nutrient-dense foods

Prioritise protein, whole grains, fruit, vegetables, dairy and healthy fats. These support your baby's growth without excess empty calories from sugary drinks and snacks.

🚶‍♀️ Stay gently active

If your doctor approves, around 150 minutes of moderate activity a week (walking, swimming, prenatal yoga) helps keep gain steady and eases aches.

🩺 Track it with your provider

Your midwife or doctor weighs you at visits and watches the trend, not a single number. Always raise any concerns about gaining too fast or too slowly with them.

How Much Weight Should You Gain in Pregnancy?

There is no single answer — the healthy amount depends on your pre-pregnancy BMI. The most widely used guidance comes from the Institute of Medicine (IOM), now the National Academy of Medicine, and is recommended by health bodies worldwide. A woman who started at a normal weight should gain about 11.5–16 kg (25–35 lb), while someone who was overweight or obese needs to gain less, and someone underweight needs to gain a little more.

When does the weight come on?

Most weight is gained in the second and third trimesters. In the first trimester many women gain very little — about 0.5–2 kg (1–4.5 lb) — and some lose a little due to nausea, which is completely normal. After about week 13, a steady weekly gain begins: roughly 0.4–0.5 kg (about 1 lb) per week for normal-weight women, and less for those who started heavier. This calculator uses those weekly rates to estimate how much you should have gained by your current week.

What if I'm above or below the range?

Don't panic if you're slightly off — these are ranges, not exact targets, and a single weigh-in matters less than the overall trend. Gaining more than recommended is linked to a higher chance of gestational diabetes, high blood pressure and a larger baby, while gaining too little can raise the risk of a small or premature baby. The best thing to do is talk through your own numbers with your midwife or doctor, who know your full health picture.

Twin pregnancies

Carrying twins means a higher healthy range — for example 16.8–24.5 kg (37–54 lb) for a normal-weight mother. Tick the twins box above to see the right range for you. Because evidence is more limited for twins (especially if you were underweight), it's even more important to follow your care team's personalised advice.

Frequently Asked Questions

How much weight should I gain during pregnancy? +

It depends on your pre-pregnancy BMI. Normal-weight women (BMI 18.5–24.9) should gain 11.5–16 kg (25–35 lb); underweight women 12.5–18 kg (28–40 lb); overweight women 7–11.5 kg (15–25 lb); and women with obesity 5–9 kg (11–20 lb).

How much should I gain each week? +

The first trimester adds about 0.5–2 kg total. After that, normal-weight women gain about 0.4–0.5 kg (≈1 lb) per week, overweight women about 0.2–0.3 kg, and women with obesity about 0.2 kg per week.

Where does pregnancy weight go? +

Only part is the baby (~3–3.5 kg). The rest is the placenta, amniotic fluid, a larger uterus and breasts, extra blood and body fluid, and fat stores your body builds to support breastfeeding.

Is it bad to gain too much or too little? +

Too much gain raises the risk of gestational diabetes, high blood pressure and a larger baby; too little raises the risk of a small or premature baby. Aim to stay within your range, but always follow your own doctor's advice.

How much weight should I gain with twins? +

Normal weight: 16.8–24.5 kg (37–54 lb); overweight: 14.1–22.7 kg (31–50 lb); obese: 11.3–19.1 kg (25–42 lb). There's no firm underweight-twin guideline, so discuss your target with your doctor.

⚕️

Medical note: This calculator gives general estimates based on IOM guidelines and is not medical advice. Every pregnancy is different — always follow the guidance of your own doctor or midwife.