The free gas in a cylinder or bank from its floodable volume in cubic feet and its pressure in psi.
The formula: Free gas = floodable volume x psi / 14.7. Change any box and the full working updates. For study only, never for dive planning.
The IMCA ADS, BDS and LST papers ask this as a four-option question, with a calculator on screen. A free account gives you 15 practice questions for each exam, each with the worked answer and the document it comes from.