Cubic kilometers to gallons (US liquid) conversion calculator above calculates how many gallons (US liquid) are in 'X' cubic kilometers (where 'X' is the number of cubic kilometers to convert to gallons (US liquid)). In order to convert a value from cubic kilometers to gallons (US liquid) (from km³ to gal) simply type the number of km³ to be converted to gal and then click on the 'convert' button.