text: how much alcohol do you mix with water to keep it from freezing?   to keep it from freezing at what temperature? for every mole of alcohol added to 1 kg of water, its freezing temperature is reduced by 1.86 degrees c. the source below tells you how to calculate the freezing temp for any consentration of alcohol in water. you can apply it to figure out how much to add to make the freezing point whatever you want.