Pregnancy Weight Gain Calculator
Use this calculator to determine your recommended weight gain during pregnancy based on your pre-pregnancy Body Mass Index (BMI) and the type of pregnancy (single or twins).
Understanding Pregnancy Weight Gain
Gaining the right amount of weight during pregnancy is crucial for both your health and your baby's development. Too little or too much weight gain can lead to complications. The recommended amount of weight gain varies based on your pre-pregnancy Body Mass Index (BMI) and whether you are carrying one baby or twins.
Why is Pre-pregnancy BMI Important?
Your pre-pregnancy BMI is a key factor because it reflects your body composition before pregnancy. It helps healthcare providers determine a personalized weight gain target. BMI is calculated using your weight and height:
BMI = weight (kg) / (height (m))^2
Or, if using pounds and inches:
BMI = (weight (lbs) / (height (inches))^2) * 703
Recommended Weight Gain Guidelines (for single pregnancies):
- Underweight (BMI < 18.5): 28-40 lbs (12.7-18.1 kg)
- Normal Weight (BMI 18.5-24.9): 25-35 lbs (11.3-15.9 kg)
- Overweight (BMI 25.0-29.9): 15-25 lbs (6.8-11.3 kg)
- Obese (BMI ≥ 30.0): 11-20 lbs (5.0-9.1 kg)
Recommended Weight Gain Guidelines (for twin pregnancies):
- Underweight (BMI < 18.5): 50-62 lbs (22.7-28.1 kg)
- Normal Weight (BMI 18.5-24.9): 37-54 lbs (16.8-24.5 kg)
- Overweight (BMI 25.0-29.9): 31-50 lbs (14.1-22.7 kg)
- Obese (BMI ≥ 30.0): 25-42 lbs (11.3-19.1 kg)
Weight Gain Distribution Throughout Pregnancy:
Weight gain isn't linear. Most women gain:
- First Trimester (Weeks 1-12): Typically 1-5 lbs (0.5-2.3 kg) total.
- Second and Third Trimesters (Weeks 13-40): A more consistent gain, usually 0.5 to 2 lbs (0.23 to 0.91 kg) per week, depending on your pre-pregnancy BMI and whether you're carrying multiples.
Factors Influencing Weight Gain:
Several factors can influence your pregnancy weight gain, including:
- Morning Sickness: Can lead to initial weight loss or slower gain.
- Appetite Changes: Cravings or aversions can impact food intake.
- Activity Level: Maintaining a healthy, active lifestyle is encouraged.
- Genetics: Family history can play a role.
- Fluid Retention: Swelling can contribute to weight.
Healthy Eating and Exercise:
Focus on nutrient-dense foods and listen to your body's hunger cues. Regular, moderate exercise, as approved by your healthcare provider, is also beneficial. Always consult with your doctor or a registered dietitian for personalized advice regarding your pregnancy weight gain.
.calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #ffffff;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
}
.calculator-container h2, .calculator-container h3, .calculator-container h4 {
color: #2c3e50;
text-align: center;
margin-bottom: 20px;
}
.calculator-container p {
line-height: 1.6;
color: #555;
margin-bottom: 15px;
}
.calculator-form .form-group {
margin-bottom: 18px;
display: flex;
flex-wrap: wrap;
align-items: center;
gap: 10px;
}
.calculator-form label {
flex: 1 1 180px;
font-weight: bold;
color: #34495e;
}
.calculator-form input[type="number"],
.calculator-form input[type="text"] {
flex: 2 1 150px;
padding: 10px 12px;
border: 1px solid #ccc;
border-radius: 5px;
font-size: 16px;
box-sizing: border-box;
max-width: 200px;
}
.calculator-form input[type="radio"] {
margin-right: 5px;
}
.unit-toggle, .radio-group {
display: flex;
align-items: center;
gap: 15px;
flex: 2 1 150px;
}
.unit-toggle label, .radio-group label {
font-weight: normal;
color: #555;
cursor: pointer;
flex: unset;
}
.calculate-button {
display: block;
width: auto;
padding: 12px 25px;
margin: 25px auto 20px auto;
background-color: #28a745;
color: white;
border: none;
border-radius: 5px;
font-size: 18px;
cursor: pointer;
transition: background-color 0.3s ease;
}
.calculate-button:hover {
background-color: #218838;
}
.calculator-result {
background-color: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 20px;
margin-top: 25px;
font-size: 17px;
color: #333;
line-height: 1.8;
}
.calculator-result h4 {
color: #007bff;
margin-top: 0;
text-align: left;
}
.calculator-result p {
margin-bottom: 10px;
}
.calculator-result strong {
color: #0056b3;
}
.article-content {
margin-top: 40px;
padding-top: 30px;
border-top: 1px solid #eee;
}
.article-content ul {
list-style-type: disc;
margin-left: 20px;
margin-bottom: 15px;
color: #555;
}
.article-content ul li {
margin-bottom: 8px;
}
.article-content code {
background-color: #eef;
padding: 2px 5px;
border-radius: 3px;
font-family: 'Courier New', Courier, monospace;
color: #c7254e;
}
function updateWeightInputs() {
var weightInput = document.getElementById('prePregnancyWeight');
var unitLbs = document.getElementById('weightUnitLbs').checked;
if (unitLbs) {
weightInput.placeholder = 'e.g., 140';
} else { // kg
weightInput.placeholder = 'e.g., 63.5';
}
}
function updateHeightInputs() {
var heightImperialDiv = document.getElementById('heightImperial');
var heightMetricDiv = document.getElementById('heightMetric');
var heightFeetInput = document.getElementById('prePregnancyHeightFeet');
var heightInchesInput = document.getElementById('prePregnancyHeightInches');
var heightCmInput = document.getElementById('prePregnancyHeightCm');
var unitImperial = document.getElementById('heightUnitImperial').checked;
if (unitImperial) {
heightImperialDiv.style.display = 'flex';
heightMetricDiv.style.display = 'none';
heightFeetInput.placeholder = 'e.g., 5';
heightInchesInput.placeholder = 'e.g., 5';
} else { // metric
heightImperialDiv.style.display = 'none';
heightMetricDiv.style.display = 'block';
heightCmInput.placeholder = 'e.g., 165';
}
}
function calculateWeightGain() {
var prePregnancyWeight = parseFloat(document.getElementById('prePregnancyWeight').value);
var currentPregnancyWeek = parseInt(document.getElementById('currentPregnancyWeek').value);
var pregnancyType = document.querySelector('input[name="pregnancyType"]:checked').value;
var weightUnitLbs = document.getElementById('weightUnitLbs').checked;
var heightUnitImperial = document.getElementById('heightUnitImperial').checked;
var resultDiv = document.getElementById('result');
resultDiv.innerHTML = ";
if (isNaN(prePregnancyWeight) || prePregnancyWeight <= 0) {
resultDiv.innerHTML = 'Please enter a valid pre-pregnancy weight.';
return;
}
if (isNaN(currentPregnancyWeek) || currentPregnancyWeek 40) {
resultDiv.innerHTML = 'Please enter a valid current week of pregnancy (1-40).';
return;
}
var prePregnancyHeightCm;
if (heightUnitImperial) {
var prePregnancyHeightFeet = parseFloat(document.getElementById('prePregnancyHeightFeet').value);
var prePregnancyHeightInches = parseFloat(document.getElementById('prePregnancyHeightInches').value);
if (isNaN(prePregnancyHeightFeet) || isNaN(prePregnancyHeightInches) || prePregnancyHeightFeet < 0 || prePregnancyHeightInches = 12) {
resultDiv.innerHTML = 'Please enter a valid pre-pregnancy height in feet and inches.';
return;
}
prePregnancyHeightCm = ((prePregnancyHeightFeet * 12) + prePregnancyHeightInches) * 2.54;
} else {
prePregnancyHeightCm = parseFloat(document.getElementById('prePregnancyHeightCm').value);
if (isNaN(prePregnancyHeightCm) || prePregnancyHeightCm <= 0) {
resultDiv.innerHTML = 'Please enter a valid pre-pregnancy height in centimeters.';
return;
}
}
var weightKg = weightUnitLbs ? prePregnancyWeight / 2.20462 : prePregnancyWeight;
var heightM = prePregnancyHeightCm / 100;
var bmi = weightKg / (heightM * heightM);
var bmiCategory = '';
var gainGuidelines;
if (bmi = 18.5 && bmi = 25.0 && bmi <= 29.9) {
bmiCategory = 'Overweight';
if (pregnancyType === 'single') {
gainGuidelines = { totalMin: 15, totalMax: 25, weeklyMin: 0.5, weeklyMax: 0.7 };
} else {
gainGuidelines = { totalMin: 31, totalMax: 50, weeklyMin: 1, weeklyMax: 1.5 };
}
} else {
bmiCategory = 'Obese';
if (pregnancyType === 'single') {
gainGuidelines = { totalMin: 11, totalMax: 20, weeklyMin: 0.4, weeklyMax: 0.6 };
} else {
gainGuidelines = { totalMin: 25, totalMax: 42, weeklyMin: 1, weeklyMax: 1.5 };
}
}
var firstTriGainMin = 1;
var firstTriGainMax = 5;
var currentRecommendedGainMin, currentRecommendedGainMax;
var unitLabel = weightUnitLbs ? 'lbs' : 'kg';
if (currentPregnancyWeek <= 12) {
currentRecommendedGainMin = (currentPregnancyWeek / 12) * firstTriGainMin;
currentRecommendedGainMax = (currentPregnancyWeek / 12) * firstTriGainMax;
} else {
var weeksIn2nd3rdTri = currentPregnancyWeek – 12;
currentRecommendedGainMin = firstTriGainMin + (weeksIn2nd3rdTri * gainGuidelines.weeklyMin);
currentRecommendedGainMax = firstTriGainMax + (weeksIn2nd3rdTri * gainGuidelines.weeklyMax);
}
var totalMinDisplay = weightUnitLbs ? gainGuidelines.totalMin : (gainGuidelines.totalMin / 2.20462);
var totalMaxDisplay = weightUnitLbs ? gainGuidelines.totalMax : (gainGuidelines.totalMax / 2.20462);
var weeklyMinDisplay = weightUnitLbs ? gainGuidelines.weeklyMin : (gainGuidelines.weeklyMin / 2.20462);
var weeklyMaxDisplay = weightUnitLbs ? gainGuidelines.weeklyMax : (gainGuidelines.weeklyMax / 2.20462);
var currentMinDisplay = weightUnitLbs ? currentRecommendedGainMin : (currentRecommendedGainMin / 2.20462);
var currentMaxDisplay = weightUnitLbs ? currentRecommendedGainMax : (currentRecommendedGainMax / 2.20462);
resultDiv.innerHTML = '
Your Pregnancy Weight Gain Recommendations:
' +
'Your Pre-pregnancy BMI:
' + bmi.toFixed(1) + ' (' + bmiCategory + ')' +
'Recommended Total Weight Gain:
' + totalMinDisplay.toFixed(1) + ' – ' + totalMaxDisplay.toFixed(1) + ' ' + unitLabel + '' +
'Recommended Weekly Gain (2nd & 3rd Trimester):
' + weeklyMinDisplay.toFixed(1) + ' – ' + weeklyMaxDisplay.toFixed(1) + ' ' + unitLabel + '/week' +
'By Week ' + currentPregnancyWeek + ', you should have gained approximately:
' + currentMinDisplay.toFixed(1) + ' – ' + currentMaxDisplay.toFixed(1) + ' ' + unitLabel + '' +
'
These guidelines are based on recommendations from the American College of Obstetricians and Gynecologists (ACOG) and the Institute of Medicine (IOM). Always consult with your healthcare provider for personalized advice.';
}
document.addEventListener('DOMContentLoaded', function() {
updateWeightInputs();
updateHeightInputs();
});