What is Capital Adequacy Ratio?

Legal Definition
Capital Adequacy Ratio (CAR), also known as Capital to Risk (Weighted) Assets Ratio (CRAR), is the ratio of a bank's capital to its risk. National regulators track a bank's CAR to ensure that it can absorb a reasonable amount of loss and complies with statutory Capital requirements.

It is a measure of a bank's capital. It is expressed as a percentage of a bank's risk weighted credit exposures.

This ratio is used to protect depositors and promote stability and efficiency of financial systems around the world.

Two types of capital are measured: tier one capital, which can absorb losses without a bank being required to cease trading, and tier two capital, which can absorb losses in the event of a winding-up and so provides a lesser degree of protection to depositors.
-- Wikipedia