To convert from P11 to P12, take the square root of the P11 value. That equals x^0.5.

To convert from P12 to P11, square the P12 value. That equals x*x or x^2.

Or if you don't want to do math....

P11	---	P12
0.05	---	0.22
0.1	---	0.32
0.15	---	0.39
0.2	---	0.45
0.25	---	0.5
0.3	---	0.55
0.35	---	0.59
0.4	---	0.63
0.45	---	0.67
0.5	---	0.71
0.55	---	0.74
0.6	---	0.77
0.65	---	0.81
0.7	---	0.84
0.75	---	0.87
0.8	---	0.89
0.85	---	0.92
0.9	---	0.95
0.95	---	0.97
1	---	1

Not sure why the Markdown codes for tables aren't working here, but I think that is reasonably legible.