First of all you can find an estimate based on your pre-pregnancy weight and height via a search in google for 'pregnancy weight calculator'
I was 54kg, 164cm pre preg (i'm not 58kg at 21 weeks) and i got an average weight gain of 13.6kg or between 11-16kg which was made up of
ME:
Uterus 1.1 kgs
Breasts 0.5 kgs
Blood 1.4 kgs
Water 1.9 kgs
Fat 3.8 kgs
Subtotal 8.6 kgs
Your baby:
Fetus 3.4 kgs
Placenta 0.7 kgs
Amniotic Fluid 0.9 kgs
Subtotal 5.0 kgs
Total 13.6 kgs

Although with my first i went from 52kg to 75kg (luckily i lost most of it and got back to 54kg, although cause my boobs grew so much i recon thats where the extra 2kgs are, lmao)