Pregnancy Weight Gain Calculator
Recommended gain by pre-pregnancy BMI and week.
Deliberate weight loss is generally not advised in pregnancy. If gain is faster or slower than expected, raise it with your midwife or obstetrician rather than dieting.
Recommended gain by week 20
4.1–5.3 kg
pre-pregnancy BMI 22.9 — Normal weight
At term the gain is roughly: baby 3-3.5 kg, placenta 0.7, amniotic fluid 0.9, blood volume 1.4, uterus and breast tissue 1.5, and fat stores 2.5-4 kg.
How the Pregnancy Weight Gain Calculator works
Recommended weight gain in pregnancy depends on where you started. The Institute of Medicine sets different ranges by pre-pregnancy BMI, because gaining too little and gaining too much both carry risks for mother and baby.
Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.
Frequently asked questions
How much weight should I gain in pregnancy?
IOM guidelines for a single baby: 12.5-18 kg if you started underweight (BMI under 18.5), 11.5-16 kg at a normal BMI, 7-11.5 kg if overweight, and 5-9 kg if obese. Twin pregnancies have separate, higher ranges.
When does most pregnancy weight gain happen?
The first trimester typically adds only 0.5-2 kg. The majority accumulates in the second and third trimesters at roughly 0.4-0.5 kg per week for someone starting at a normal BMI, and less for those starting higher.
What is the weight actually made of?
At term, roughly: baby 3-3.5 kg, placenta 0.7 kg, amniotic fluid 0.9 kg, increased blood volume 1.4 kg, uterus and breast tissue 1.5 kg, and fat stores 2.5-4 kg. The fat is a normal energy reserve for breastfeeding, not something to be avoided.
Should I diet if I am gaining too fast?
Not without medical guidance. Deliberate weight loss is generally not advised in pregnancy. The usual approach is to slow the rate of gain through food quality and gentle activity, supervised by your midwife or obstetrician.