If volume - 1 US teaspoon = 0.17 ounces US<br />If weight - it depends of the density of your foodstuff. For example<br />1 US teaspoon of water = 0.17 oz<br />1 US teaspoon of buckwheat = 0.15 oz<br />1 US teaspoon of honey = 0.23 oz and so on.
Comparison of Letter (shaded light blue) and Government letter sizes with some similar paper and photographic paper sizes. Letter or US Letter is a paper size commonly used as home or office stationery in Canada, the United States, Mexico and the Dominican Republic. It measures 8.5 by 11.0 inches (215.9 by 279.4 mm). US Letter size paper is a standard defined by the American National Standards Institute (ANSI), in contrast to the A4 paper used by all other nations, which is defined by the International Organization for Standardization (specifically, in ISO 216).
The difference between US Letter and Legal Paper sizes and international A4 is discussed here, however it is important to say that Letter is effectively the equivalent to A4 size in the USA.