As a star ages it slows its rotation and diminishes the amount of magnetic activity in its chromosphere. Hence the measured emission from the chromosphere can be used to estimate the age of a star, particularly for F and G-type dwarf stars with an age of less than two billion years. However, this technique becomes less accurate for ages beyond about 5.6 billion years. Based upon the chromosphere emission of HD 12661, it is older than the Sun with an estimated age of roughly seven billion years. It has a low projected rotational velocity of 1.20 km/s, consistent with it being an older star. The age of a star can also be estimated by the abundance of lithium, as this element is destroyed through thermonuclear fusion at the core. However, this is less accurate technique. For HD 12661, the lithium abundance gives an age estimate of 4.4 billion years.