250 grams is about 500ml(50cl/5dl/0,5l). (One 100milliliters of flour weights about 50 grams)

You have to know the density of flour first.

Let 's say it is 1,4 g/ml

Then 250g :1,4 g/ml = 178,6 ml.

Let 's say it is 1,4 g/ml

Then 250g :1,4 g/ml = 178,6 ml.