To convert kg to US gallons, use the following formula:
\[ \text{Gallons} = \frac{\text{kg}}{3.785412 \times \text{density}} \]
To convert US gallons to kg, use the following formula:
\[ \text{kg} = \text{gallons} \times 3.785412 \times \text{density} \]
Where density is in g/ml.