Short answerIn a foam cooler, dry ice loses roughly 5 to 10 pounds every 24 hours, per UPS. A thicker cooler, a closed lid and less empty space make it last longer.
How much to buy
Multiply the days you need by 5 to 10 pounds. Buy toward the high end for a thin cooler, hot weather or a lid you will open often.
- 1 day: about 5–10 lb
- 2 days: about 10–20 lb
- 3 days: about 15–30 lb
- 5 days: about 25–50 lb
Make it last longer
- Use the thickest cooler you have. UPS notes that lower-density foam lets it sublimate faster.
- Fill empty space with crumpled paper so less air circulates.
- Open the lid as little as possible.
- Buy it as close to when you need it as you can. It starts shrinking from the moment you buy it.
Why it shrinks
Dry ice does not melt into water. It turns straight from solid into carbon dioxide gas, which is called sublimation. That gas is why the cooler must never be sealed airtight.
Sources (checked October 27, 2026)
General guidance, not professional safety advice. Follow your supplier’s and carrier’s instructions.