Postpartum Weight Loss Calculator
Use this postpartum weight loss calculator to see how much weight you carry compared with before pregnancy and a gentle pace to get back.
Updated October 2, 2026
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Postpartum Weight Retention Is Calculated
Postpartum weight retention is the difference between your weight now and your weight before you got pregnant. It is a simple gap, not a grade. This calculator measures that gap, then shows a cautious pace and a time range for closing it, based on how you feed your baby.
What Postpartum Weight Retention Measures
It measures how far your current weight sits above or below your pre-pregnancy weight. It does not say how much is fat, muscle, or fluid, and it does not measure your health.
The Formula
Weight retained = current weight minus pre-pregnancy weight
Time range = weight retained divided by pace of loss (shown as a low and a high end)
The weight you are compared against is your own starting point. Pregnancy weight gain guidelines from the Institute of Medicine (now part of the National Academies) in 2009 set the ranges used if you add your height and pregnancy gain¹.
How This Calculator Computes Your Result
You enter your pre-pregnancy weight, current weight, weeks since delivery, and how you feed your baby (not breastfeeding, partly breastfeeding, or exclusively breastfeeding). You can use kilograms or pounds. Three inputs are optional: weight gained in pregnancy, height, and the week you delivered.
We subtract to get your retained weight, rounded to 0.1 kg. Then we pick a pace range from your feeding choice and divide your retained weight by the slow and fast ends of that range. The time estimate starts from 6 weeks after delivery. If you are earlier than that, you still see your retained weight, but no time estimate. The calculator never gives a calorie target.
What Your Result Means
Your pace range depends on how you feed your baby. The ranges are set on the cautious side of published guidance³ ⁵.
Feeding | Pace of loss per month | About per week |
Not breastfeeding | 1.0 to 3.0 kg (2.2 to 6.6 lb) | 0.23 to 0.69 kg |
Partly breastfeeding | 1.0 to 2.0 kg (2.2 to 4.4 lb) | 0.23 to 0.46 kg |
Exclusively breastfeeding | 0.5 to 1.5 kg (1.1 to 3.3 lb) | 0.12 to 0.35 kg |
Your retained weight is shown in one of these ways:
Your result | What the calculator shows |
At or below pre-pregnancy weight | No loss needed, with a kind note |
Under 1 kg above | Within everyday scale swings, no time estimate |
1 kg or more above, under 6 weeks postpartum | Retained weight only, no pace or timeline yet |
1 kg or more above, 6 weeks or later | Retained weight, pace range, and a time range in months |
If you add height, pregnancy gain, and delivery week (37 weeks or later), you also see whether your pregnancy gain was below, within, or above the 2009 range for your starting BMI. For a baby born at term, those ranges are 28 to 40 lb if underweight, 25 to 35 lb if normal weight, 15 to 25 lb if overweight, and 11 to 20 lb if obese¹.
What the Research Says About Retained Weight
Weight gained in pregnancy plays a part. A meta-analysis of nine studies and over 65,000 women found that women who gained more than the guidelines suggest kept about 3 kg more after 3 years than women who gained within them². That is an average, and it says nothing about you as a person.
A Cochrane review of 14 trials found that diet, or diet plus exercise, helped women lose more weight after birth (about 1.7 to 1.9 kg more than usual care). Exercise alone did not move the scale on its own. The review saw no harm to breastfeeding but asked for more evidence⁴.
Why a Slow Pace Matters While Breastfeeding
In a trial of 40 overweight breastfeeding women, losing about 0.5 kg a week from week 4 postpartum did not slow their babies' growth³. That is a ceiling for one group of women, not a target for everyone, so the ranges above stay lower. The Academy of Nutrition and Dietetics says a slow loss of about 1 pound a week is a safe goal while breastfeeding, and that eating under 1,800 calories a day may reduce milk supply⁵. Because of this, the calculator gives no calorie numbers.
A Note on Accuracy
This is an educational estimate, not medical advice. Real weight loss is uneven and often stalls. The key breastfeeding study was in overweight, healthy women, and the ranges assume one baby, not twins or more. Pre-pregnancy weight is often recalled from memory, which adds error. Recovery from a cesarean birth or a complicated delivery can change what is safe, so talk to your doctor or midwife before changing your eating or exercise. The postpartum check-up, due no later than 12 weeks after birth, is a good time to ask⁶.
Frequently Asked Questions
How long does it take to lose pregnancy weight?
It varies a lot. For 6 kg retained, this calculator shows about 4 to 12 months if you are exclusively breastfeeding and 2 to 6 months if you are not. Taking longer is common.
How much weight can I lose per week while breastfeeding?
A study of overweight breastfeeding women found about 0.5 kg per week did not affect infant growth³, and this calculator stays below that, at 0.12 to 0.35 kg per week for exclusive breastfeeding. Talk to your care provider if you want to go faster.
Is it normal to weigh more than before pregnancy after giving birth?
Yes. Many women stay above their pre-pregnancy weight for months or longer, and how much is kept is linked to pregnancy weight gain². Under 1 kg is within normal day to day change.
How accurate is a postpartum weight loss calculator?
It is an estimate. It uses ranges from research and cannot know your health, feeding pattern, or recovery. Use it as a rough guide and a starting point for a talk with your care provider⁶.
Sources
Pregnancy Weight Gain Recommendations, CDC (based on Institute of Medicine, 2009)
Gestational Weight Gain and Long-Term Postpartum Weight Retention, Nehring et al., 2011
The Effect of Weight Loss in Overweight, Lactating Women on the Growth of Their Infants, Lovelady et al., 2000
Diet or Exercise, or Both, for Weight Reduction in Women After Childbirth, Amorim Adegboye and Linne, 2013
Losing Weight While Breastfeeding, Academy of Nutrition and Dietetics
Optimizing Postpartum Care, ACOG Committee Opinion 736, 2018