How to read the pregnancy gain range
Start from pre-pregnancy BMI and gestational week.
Use pre-pregnancy weight
Enter the weight before conception rather than the current weight.
Find the BMI band
The category determines the total range shown in kilograms and pounds.
Check the week
The weekly estimate shows where the total range roughly sits at this stage of pregnancy.
What does this tool do?
The Institute of Medicine links recommended gain to pre-pregnancy body mass index. This calculator applies those singleton ranges and estimates how much of the total range typically applies by a given week.
The Formula
Pre-pregnancy BMI = weight ÷ height²; recommended total gain from the IOM BMI band; early gain 0.5–2 kg by week 13Frequently Asked Questions
What if I am expecting twins?
Twin pregnancies have higher targets and closer monitoring. The singleton ranges shown here do not apply; follow the plan from your obstetric team.
How much gain is typical in the first trimester?
About 0.5–2 kg in total by week 13 is common. Nausea and appetite can change this, and clinicians usually look at the trend rather than one measurement.