Converting barometric pressure to absolute pressure

• 1). Determine the units in which the barometric pressure is given. For millimeters of mercury, or mm Hg, go to Step 2. For inches of mercury, see Step 3. For feet of water, see Step 4, and for millibars or bars, see Step 5.
  
  
• 2). Multiply the barometric pressure in mm Hg by 133. The result is the absolute pressure in pascals.
  
  
• 3). Multiply the barometric pressure in inches mercury by 3,386. The result is the absolute pressure in pascals.
  
  
• 4). Multiply the barometric pressure in feet of water by 2,989 to get the absolute pressure in pascals.
  
  
• 5). Multiply the pressure in millibars by 100 to get the absolute pressure in pascals. For bars, multiply by 100,000.