One ounce is equal to 28.3 grams. Therefore, half of an ounce is equal to approximately 14.2 grams. This is assuming the ounce is for solid mass measurement, rather than the fluid ounce for liquid.
The ounce is a common small unit of solid mass measurement within the United States customary and British Imperial systems, while the gram is the common small unit of measurement used in the metric system, which is generally used more commonly around the world as a whole. The multiplier to convert metric units to imperial units, or vice versa, is not a constant number, because the ratios between the two systems are generally arbitrary.