How Much Ice Do You Actually Need?

Ice is the single most under-bought item at any gathering, and it is not close.

Nobody plans badly on purpose. It happens because ice does not feel like a real item. It has no recipe, it costs almost nothing, and buying it is the last thing you do. So it gets a vague mental note instead of a number — and vague mental notes are how you end up sending someone to a petrol station at nine o'clock.

The number

One pound per person, for drinks alone.

That is for putting ice in glasses over an evening. It assumes a normal mixed crowd and a normal-length gathering.

Two pounds per person if any of these are true:

• You are chilling bottles or cans in a tub or cooler
• It is warm out, or the room will get warm
• It is going to run longer than about four hours
• You are making anything blended or shaken

A standard bag is around seven pounds. So for twelve people at a backyard dinner where the drinks are in a tub, you want roughly twenty-four pounds — three and a half bags. Buy four.

Why chilling eats so much more

Ice in a glass has one job and melts slowly. Ice in a tub full of warm bottles is doing thermodynamics. It is absorbing heat out of every bottle you put in, and then out of the air, and then out of the tub itself if the tub was sitting in the sun.

A cooler of warm cans will burn through a bag of ice before anyone has had a drink. If you can, chill the drinks in a fridge first and use ice to keep them cold rather than to get them cold. That one change roughly halves the ice you need.

Buy it last, and buy it separately

Ice bought at the start of a shop spends forty minutes in a warm trolley and then a car. Make it the final stop.

If you are buying a lot, it is worth knowing that most large bags are sold by weight and stack badly. Four bags take up more freezer than you think — which is the other reason people under-buy. There is nowhere to put it.

Which brings us to the real constraint.

You do not need freezer space. You need a bucket.

You are not storing ice. You are holding it for a few hours.

Anything insulated works: a cooler, a cool bag, a stock pot with a towel over it, a plastic tub inside another plastic tub. Put it somewhere out of the sun and it will be fine for the length of a gathering.

A bag of ice sitting in a sink will be water by the time people arrive. A bag of ice in a covered cooler will still be ice at the end of the night.

The one to remember

If you take nothing else: buy more than you think, buy it last, and keep it covered.

It is the cheapest way to avoid the only errand nobody wants to run after guests have already arrived.