Convert ml to liters (ml to L)

One milliliter is exactly 0.001 liters, by the prefix. The milliliter is also exactly one cubic centimeter, which is why medical and engineering writing uses ml and cc interchangeably and both are right.

Worked through: 250 ml x 0.001 = 0.25 L.

Going the other way, one liter is 1,000 milliliters.

For mental arithmetic: Move the decimal point three places left.

The ml-to-liter step is trivial and the cc equivalence is the part worth carrying away: 1 ml is 1 cm3, so a 500 ml bottle holds 500 cubic centimeters and a 2.0-liter engine displaces 2,000 cc. Engine specifications use cc and laboratory work uses cm3, both for the same quantity as the milliliter. A teaspoon is nominally 5 ml and a tablespoon 15 ml, but kitchen spoons are not calibrated instruments and hold those volumes only approximately.

Precision is worth matching to the input. A measurement given as 5 ml carries one or two significant figures, and reporting its conversion to six implies a precision the original never had.