Pregnancy Weight Gain Calculator
Your Pregnancy Weight Gain Tracker
Recommended Weight Gain So Far
About Your Recommendation
This recommendation is based on the Institute of Medicine (IOM) guidelines for a healthy pregnancy. This is the healthy range you should aim for by week --.
These recommendations are for informational purposes. Always follow the personalized advice of your doctor or healthcare provider regarding your pregnancy weight gain.
What is a Pregnancy Weight Gain Calculator?
A Pregnancy Weight Gain Calculator is a tool that provides a recommended weight gain schedule throughout your pregnancy. It uses your pre-pregnancy height and weight to calculate your Body Mass Index (BMI) and then determines your healthy weight gain range based on the official guidelines from the Institute of Medicine (IOM).
Gaining a healthy amount of weight during pregnancy is crucial for both your health and your baby's. Gaining too little can increase the risk of a low birth weight, while gaining too much can increase risks of gestational diabetes, high blood pressure, and complications during delivery. This calculator helps you track your progress against these authoritative guidelines.
How the Calculator Works: IOM Guidelines
The calculator's logic is based on the IOM's recommendations, which are the standard used by doctors. The calculation is a two-step process:
Step 1: Calculate Your Pre-Pregnancy BMI
First, your pre-pregnancy weight and height are used to find your BMI, which places you into one of four categories.
- BMI = (Weight in kg) / (Height in meters)²
Step 2: Determine Your Recommended Weight Gain
Based on your BMI category and whether you are carrying a singleton or twins, the calculator provides a total recommended gain and a weekly rate of gain for the second and third trimesters.
| Pre-Pregnancy BMI Category | Recommended Total Gain (Singleton) | Recommended Total Gain (Twins) |
|---|---|---|
| Underweight (BMI < 18.5) | 12.5 - 18 kg (28 - 40 lbs) | 22.7 - 28 kg (50 - 62 lbs) |
| Normal Weight (BMI 18.5 - 24.9) | 11.5 - 16 kg (25 - 35 lbs) | 17 - 25 kg (37 - 54 lbs) |
| Overweight (BMI 25.0 - 29.9) | 7 - 11.5 kg (15 - 25 lbs) | 14 - 23 kg (31 - 50 lbs) |
| Obese (BMI ≥ 30.0) | 5 - 9 kg (11 - 20 lbs) | 11 - 19 kg (25 - 42 lbs) |
Example Calculation
- Pre-Pregnancy Weight: 65 kg (143 lbs)
- Height: 168 cm (5' 6")
- Pregnancy: Singleton
- Current Week: 20
Calculation:
1. BMI: 65 / (1.68 * 1.68) = 23.0. This is a "Normal Weight" category.
2. Total Gain (Normal): 11.5 - 16 kg.
3. 1st Trimester Gain: 0.5 - 2 kg (by week 13).
4. Weekly Gain (Trimesters 2 & 3): 0.35 - 0.5 kg per week.
5. Gain at Week 20: (0.5 to 2 kg) + (7 weeks * 0.35 to 0.5 kg) = 2.95 kg to 5.5 kg.
Pregnancy Weight Gain FAQs
It's not just "baby weight." At the end of a full-term pregnancy, the weight is typically distributed as follows:
- Baby: ~3.5 kg (7.5 lbs)
- Placenta: ~1 kg (2-3 lbs)
- Amniotic Fluid: ~1 kg (2-3 lbs)
- Increased Uterus Size: ~1 kg (2-3 lbs)
- Increased Breast Tissue: ~1 kg (2-3 lbs)
- Increased Blood Volume: ~2 kg (4 lbs)
- Maternal Fat Stores: ~3 kg (7 lbs)
It is very common to gain very little, or even lose weight, in the first trimester (weeks 1-13). This is often due to morning sickness, nausea, and food aversions. For a person with a normal BMI, the recommended gain in the entire first trimester is only 0.5 - 2 kg (1-4.5 lbs). Most of the essential weight gain occurs in the second and third trimesters. Always discuss your concerns with your doctor, but minimal gain in the beginning is usually not a cause for alarm.
A twin pregnancy requires significantly more weight gain because you are supporting the growth of two babies, two placentas (or one larger one), and more amniotic fluid. Gaining the appropriate amount of weight in a twin pregnancy is crucial for reducing the risk of preterm birth and ensuring both babies have a healthy birth weight. Your doctor will monitor your gain closely.
Yes. Even if you are in the overweight or obese BMI category, it is still recommended to gain weight, as shown in the table above (e.g., 7 - 11.5 kg for overweight). Pregnancy is *not* a time to try to lose weight. Gaining the recommended amount supports your baby's growth and the necessary changes in your body (placenta, blood volume, etc.). Your doctor can provide a personalized plan to help you gain a healthy amount.