Watt seconds to British thermal units (IT) conversion calculator shown above calculates how many British thermal units (IT) are in 'X' watt seconds (where 'X' is the number of watt seconds to convert to British thermal units (IT)). In order to convert a value from watt seconds to British thermal units (IT) (from Ws to BTU) type the number of Ws to be converted to BTU and then click on the 'convert' button.