One teaspoon of liquid equals 5 ml, meaning 1 ml equals one-fifth of a teaspoon. There are 1,000 ml in one liter of liquid.
The smallest quantity of liquid in the metric system is one milliliter, usually written as 1 ml, which is a thousandth of a liter. A liter is the base measure of liquid and is the equivalent of 32 fluid ounces, one quart or about four cups. One cup of liquid is about 250 ml. Dry quantities vary from liquid quantities in the metric system and are measured in grams and kilograms. A typical cup of flour is equivalent to nearly 250 grams, and a kilogram of all-purpose flour is equivalent to about eight cups.