1 US teaspoon (tsp) = 0.02083333333 US cup (c) = 4.92892159 milliliters (ml) = 1/3 US tablespoons (tbsp) = 1/6 US fluid ounce (fl. oz.). The teaspoon is rounded to precisely 5 mL and cup is rounded to 240 millilitres by US federal regulations for food labeling purposes.