Commonly used quantity: length unit, millimeter, centimeter, decimeter, meter, kilometer (kilometer). Unit of weight, grams, kilograms (kilograms), tons. Area unit, square millimeter, square centimeter, square decimeter, square meter, square kilometer, hectare. Unit of volume, cubic centimeter, cubic decimeter, cubic meter. Unit of volume, milliliter, liter. Time unit, year, month, day, hour, minute and second.