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Calculate pregnancy weight gain by week with our Pregnancy Weight Gain Calculator. Check BMI, expected gain, and recommended weight ranges in kg.
| Pre-Pregnancy BMI | Category | Total Gain | 2nd/3rd Tri Rate |
|---|---|---|---|
| < 18.5 | Underweight | 28–40 lb (12.5–18 kg) | 1.0–1.3 lb/wk (0.44–0.58 kg/wk) |
| 18.5–24.9 | Normal Weight | 25–35 lb (11.5–16 kg) | 0.8–1.0 lb/wk (0.35–0.50 kg/wk) |
| 25.0–29.9 | Overweight | 15–25 lb (7–11.5 kg) | 0.5–0.7 lb/wk (0.23–0.33 kg/wk) |
| ≥ 30.0 | Obese | 11–20 lb (5–9 kg) | 0.4–0.6 lb/wk (0.17–0.27 kg/wk) |
Pregnancy weight gain is a normal part of a healthy pregnancy. It supports your baby’s growth and helps your body prepare for birth. But the right amount of gain can vary from person to person.
Our Pregnancy Weight Gain calculator helps you estimate weight gain based on your pre-pregnancy BMI and current pregnancy week. You can enter your height, pre-pregnancy weight, current weight, and gestational week. The calculator then shows your BMI, actual weight gain, expected gain, and result range.
This tool is designed mainly for singleton pregnancy. It uses the IOM and CDC pregnancy weight gain ranges.
The first step is to calculate your pre-pregnancy BMI.
BMI = Pre-pregnancy weight (kg) ÷ [Height (m) × Height (m)]
If you use pounds and inches, use:
BMI = [Weight (lb) × 703] ÷ Height (in)²
Next, calculate your actual pregnancy weight gain.
Actual Weight Gain = Current Weight − Pre-pregnancy Weight
For example, if your pre-pregnancy weight was 60 kg and your current weight is 68 kg:
Actual Weight Gain = 68 − 60 = 8 kg
Your BMI then sets the recommended pregnancy weight gain range.
| Pre-pregnancy BMI | Category | Total Gain | 2nd & 3rd Trimester Weekly Gain |
|---|---|---|---|
| Less than 18.5 | Underweight | 12.5–18 kg | 0.44–0.58 kg |
| 18.5–24.9 | Normal weight | 11.5–16 kg | 0.35–0.50 kg |
| 25.0–29.9 | Overweight | 7–11.5 kg | 0.23–0.33 kg |
| 30 or higher | Obese | 5–9 kg | 0.17–0.27 kg |
For the first trimester, the calculator uses an approximate gain range of 0.5–2 kg. After week 13, it estimates the expected range from the BMI-based weekly rate.
Expected Low Gain = 0.5 + (Low Weekly Rate × [Current Week − 13])
Expected High Gain = 2.0 + (High Weekly Rate × [Current Week − 13])
The calculator compares your actual gain with this expected range.
Using our calculator is simple.
Suppose a pregnant woman has these values:
Height = 165 cm
Pre-pregnancy weight = 60 kg
Current weight = 70 kg
Pregnancy week = 28
First, convert height:
165 ÷ 100 = 1.65 m
Now calculate BMI:
BMI = 60 ÷ (1.65 × 1.65)
BMI = 22.04
A BMI of 22.04 falls in the normal-weight category.
Now calculate actual weight gain:
Actual Gain = 70 − 60
Actual Gain = 10 kg
At week 28:
Weeks after week 13 = 28 − 13 = 15 weeks
For normal pre-pregnancy BMI, the weekly rate is 0.35–0.50 kg.
Expected low gain:
0.5 + (0.35 × 15) = 5.75 kg
Expected high gain:
2.0 + (0.50 × 15) = 9.50 kg
So the estimated range is:
5.75–9.50 kg
The actual gain is 10 kg. Therefore, the calculator places the result above the estimated range.
This result does not diagnose a health problem. Your doctor or midwife should assess weight gain along with your pregnancy history and overall health.
Pregnancy weight gain changes as pregnancy progresses. Gain is often small in the first trimester. It usually becomes more steady during the second and third trimesters.
A pregnancy weight gain calculator by week gives a more useful estimate than looking only at total pregnancy gain. Your pre-pregnancy BMI is important because recommended gain differs for underweight, normal-weight, overweight, and obese categories.
A pregnancy weight gain calculator twins needs different weight-gain targets from a singleton pregnancy. Twin and higher-order pregnancies have different recommended ranges.
The calculator described here uses the singleton IOM ranges. Its current multiple option does not apply separate twin targets. Therefore, it should not be used to estimate recommended weight gain for twins.
For metric users, pregnancy weight gain is calculated directly in kilograms.
Weight Gain (kg) = Current Weight (kg) − Pre-pregnancy Weight (kg)
You can also convert pounds to kilograms:
Weight (kg) = Weight (lb) × 0.45359237
This makes the calculator useful as a pregnancy weight gain calculator kg tool.
If you want to calculate weight gain as a percentage of starting body weight, use:
Weight Gain Percentage = [(Current Weight − Starting Weight) ÷ Starting Weight] × 100
For example:
Starting weight = 60 kg
Current weight = 66 kg
Percentage Gain = [(66 − 60) ÷ 60] × 100
= 10%
This is a general weight gain percentage calculator formula. It is different from the pregnancy-specific BMI and weekly gain assessment.
Pregnancy weight gain and infant weight gain are different calculations. A weight gain calculator newborn or infant weight gain calculator should use the baby's age, birth weight, current weight, and growth pattern.
For daily infant gain, a simple calculation is:
Weight Gain Per Day = (Current Weight − Previous Weight) ÷ Number of Days
For example, if a baby gains 210 grams over 14 days:
210 ÷ 14 = 15 grams per day
This can help calculate grams per day weight gain, but infant growth should be assessed using age- and sex-specific growth charts. A newborn's feeding, health, gestational age, and growth pattern also matter.
Our Pregnancy Weight Gain calculator makes pregnancy weight gain easier to understand. It calculates pre-pregnancy BMI, actual weight gain, and an estimated gain range by pregnancy week.
The main formula is simple:
Actual Weight Gain = Current Weight − Pre-pregnancy Weight
The expected range then depends on your pre-pregnancy BMI and pregnancy week. Remember that the calculator is an estimate. It doesn't replace advice from your doctor or midwife.
A Pregnancy Weight Gain calculator estimates pregnancy weight gain using pre-pregnancy BMI, current weight, height, and gestational week.
Subtract your pre-pregnancy weight from your current weight.
Pregnancy Weight Gain = Current Weight − Pre-pregnancy Weight
The recommended total gain depends on your pre-pregnancy BMI. For a normal BMI, the IOM range is about 11.5–16 kg for a singleton pregnancy.
The current calculator uses singleton pregnancy targets. Twin pregnancies need separate recommended weight-gain ranges.
Yes. Enter your weight in kilograms when using metric mode. The calculator reports pregnancy weight gain in kg.
No. Pregnancy weight gain and infant weight gain use different methods. Newborn growth should be assessed with appropriate infant growth standards.
Use:
Weight Gain Per Day = Weight Change ÷ Number of Days
This formula is useful for tracking infant or newborn weight changes.