I'd suggest using kilopascals and mmHg instead of psi/bar /inHG..
http://www.chemsoc.org/exemplarchem/entries/pkirby/exemchem/Nomograph/Nomograph.html
There is also Imperial-version of this... I won't search it down.
Did you try to search google for words "psi inch hg"?
Here's good table for high vacuum:
http://www.lds-vacuum.com/conversion.html
1 micron (u) Hg = 0.001 mm Hg = 10-3 mm Hg
1 millitorr = 1 micron (u) Hg = 0.01 mm Hg
1 millibar (international) = 0.75 mm Hg
1 bar (international) = 106 dyne /cm2 - 29.53 inches Hg
1 barye = 1 dyne/ cm2
1 newton/m2 (pascal) = 10 dyne/ cm2 = 7.5x10-3 torr
1 newton/m2 (pascal) = 7.5 millitorr = 7.5 micron
1 millimeter Hg = 1000 microns = 10-3 microns = 1 torr
1 millimeter Hg =1.333 millibar = 133.3 newton /m2
1 millimeter Hg = 0.03937 inches Hg = 0.01934 psi
1 torr = 1 mm Hg = 133.3 newton/m2
1 atmosphere = 760 torr = 14.7 psi
1 psi = 2.036 inches Hg @ 32oF = 51.72 torr
1 psi = 2.041 inches Hg @ 58.4oF
1 inch Hg @ 32oF = 0.4912 psi
29.921 in Hg @ 32oF = 14.696 psi = 760 torr
30.00 in Hg @ 58.4oF = 14.696 psi = 760 torr
And the answerfor your question is: 40psi = 81,44 Inches Hg @ 32'F