The cup is about 70% filled with ice before the drink goes in. I work in hospice and drive around to patients homes all day. I’ll occasionally hit McDonald’s in the morning as I start my day (bacon, egg and cheese bagel with a large coke zero sugar.) Unless my car is getting hot in the middle of summer, that drink will last about 4 hours with some ice left over. If it’s hot enough out to melt faster, well, I’m probably drinking it faster anyway because it’s hot out.