According to Fact Monster, two thirds as a decimal is 0.666 repeating (or 0.667 rounded) and as a percent is 66.6% repeating or 66.7%. To convert the two-thirds fraction to a decimal, simply divide the top number by the bottom number, or divide 2 by 3.
To convert the decimal to the percentage, multiply the decimal by 100 and add a percentage sign. The easiest way to do this is to move the decimal point 2 places to the right. Doing so converts 0.667 to 66.7%.
Other common fraction to decimal and percentage conversions include one-fourth to 0.25 and 25%, one-third to 0.333 and 33.3% and one-half to 0.50 and 50%.