A tablespoon (tbsp) is a volume unit equal to 3 teaspoons. An ounce (oz) is a weight unit equal to 28.35 grams. To convert tbsp into oz, you need to know the density of the substance being measured. For example, 1 tbsp of water weighs approximately 0.5 oz, while 1 tbsp of butter weighs approximately 0.4 oz.