128 ounces in a gallon! This table will be useful in converting ounces to gallons, remembering how many ounces in a quart, or how many ounces in a tablespoon. If you have trouble remembering how many ounces to use, try printing this list and keeping it in your kitchen.Not all tablespoons are the same.The British tablespoon is 17.7 ml while the American tablespoon is 14.2 ml.f you have trouble remembering how many ounces to use, try printing this list and keeping it in your kitchen. Not all tablespoons are the same. The British tablespoon is 17.7 ml while the American tablespoon is 14.2 ml.