It's hard to say. When I was on 380mg/day of methadone, I would take 240mg in the morning as soon as I woke up, then another 140mg in the late afternoon, yet every morning I woke up in pretty mild but clearly noticeable withdrawal. I would wake up in withdrawal, feeling cold and uncomfortable, and immediately gobble up 24 pills of the 10mg methadone tablets (which isn't fun because they aren't small, and tend to crumble), and then I would just wait around feeling uncomfortable for around 90 minutes until I finally started to warm up.
So for me the answer is 110% of my total dose in a sense. It's sort of a black hole for me.
When I was in Australia and ran out of my methadone supply, I had to go to a local methadone clinic, and the most they'd give me was 180mg, which is around 45% of my 380mg dose. Needless to say, I got pretty sick.