The density of fat is about 0.9 grams/ml
We may convert this into pounds / cm³
0.9 grams/ml * 1 lb / 454 grams * 1 ml / 1 cm³= 0.002 lb/cm³
Next, we use the formula:
Density = mass / volume
Volume = mass / density
Volume = 11.4 / 0.002
Volume = 5,700 cm³
The person will have gained 5,700 cm³ of volume