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Dictionary of Units / Measurements

# Pressure or Stress

The S I unit of pressure is the pascal. The units of pressure are defined in the same way as those for stress - force/unit area. To change any of these other units of pressure (or stress) into their equivalent values in pascals use the operation and conversion factor given. Those marked with # are exact. Other values are given to an appropriate degree of accuracy. Measures based on water assume a density of 1 kg/liter - a value which is rarely matched in the real world, though the error is small.

 atmospheres            x 101 325 # bars                   x 100 000 # centimetres of mercury x 1333.22 centimetres of water   x 98.066 5 # feet of water          x 2989.066 92 # hectopascals [hPa]     x 100 # inches of water        x 249.088 91 # inches of mercury      x 3386.388 kg-force/sq.centimetre x 98 066.5 # kg-force/sq.metre      x 9.806 65 # kilonewton/sq.metre    x 1000 # kilopascal [kPa]       x 1000 # kips/sq.inch           x 6 894 760 meganewtons/sq.metre   x 1 000 000 # metres of water        x 9806.65 # millibars              x 100 #   pascals [Pa]           1   millimetres of mercury x 133.322 millimetres of water   x 9.806 65 # newtons/sq.centimetre  x 10 000 newtons/sq.metre       1 newtons/sq.millimetre  x 1 000 000 # pounds-force/sq.foot   x 47.880 pounds-force/sq.inch   x 6894.757 poundals/sq.foot       x 1.448 16 tons(UK)-force/sq.foot x 107 252 tons(UK)-force/sq.inch x 15 444 256 tons(US)-force/sq.foot x 95 760 tons(US)-force/sq.inch x 13 789 500 tonnes-force/sq.cm     x 98 066 500 # tonnes-force/sq.metre  x 9806.65 #