The physical presence calculator is for permanent residents applying for grant citizenship under subsection 5(1). It is found on the website of Citizenship and Immigration Canada.
You can use the calculator to find out if you have been physically present in Canada long enough to be eligible for citizenship. If you have, the calculator will tell you that you are eligible to apply. If you have not, it will tell you when you will be eligible to apply.
This online calculator is the preferred method to calculate your physical presence in Canada.