A konjac will not flower until after its 3rd growing season. so it must be 3 years old or older and about 5.5 or 6 inches or bigger. These are the facts.
By the way, that is one hell of a confusing question that almost border lines on insanity.

ironious,

Sorry if the question was confusing. It should be simple but it is difficult to both ask and to get clear answers for.

However, I think the question is important. If you think you can rewrite it, please do.

I would change a couple things myself: delete the first two paragraphs. We are encouraged not to repeat questions on this forum; I was trying to indicate that it had not been fully answered. I also wanted to indicate that I was looking for guesses, not exact probabilities.

Delete the part about supermarket tubers. It's the season for that around here, and I do have questions. I should have written a separate question.

Back to the question: I would point out a great thread by krstofer. Perhaps he can elaborate here--his thoughts and experiences would be appreciated.

http://forums.gardenweb.com/forums/load/aroid/msg011155187431.html

"They range from 2.5" to about 6" or so- Before they shrunk during blooming, that is:"

[you'll have to scroll down a bit to find this]

Also:

"8 this year- Last year two bloomed, a little tiny one & my biggest."

On the same thread, different post, by konjacking:

"MY rule is if you dont know the age... about an inch per year... so as for a 3" diameter bulb is about 3 years old... a 4" is four years and 5" is five years etc. Konjac needs to be about 5 years old to bloom, so SusanI would say after two more years of growing you may have a bloomer."

So hopefully you can see that the question is in fact a bit complex. People have different experiences and opinions. I was hoping to simplify that yet still encourage people to elaborate.

Now this is how I interpret your previous post:

% possible blooms at a given size (again these are guesses)

A) 3 inches: 0%
B) 4 inches: 0%
C) 5 inches: 0%
D) 6 inches: blooming size (% that actually bloom is unclear--clarify if I missed this.)
E) 7 inches: blooming size (again % unclear)

5 or 6 inches as blooming size is a number I've seen before. 3 years to get there is pretty quick growth. Is it from those dime size tubers? (I know large tubers put off larger offsets) Is this typical? If not I'm curious how you do it. Again, what percent of blooming size > 5 1/2 inches will actually bloom is important, especially say to someone buying these things off Ebay. Is there absolutely no chance a tuber of some unspecified age that's 4-5 inches in diameter will bloom?

Hopefully you can see why I tried to simply all of this.

Again, I would love to get krstofer's thoughts on this, because unless I misunderstood his comments, his experiences fly in the face of conventional wisdom.

I have yet to see someone try to list a large number of their tubers by size and first bloom--that would also be interesting.

I do think people on this forum have a tremendous amount of information and experiences--the question is how to combine it and make sense of it.

okay Id say
3 inches: 10%
4 inches: 20-40%
5 inches: 70-90%
6 inches: 95-100%
7 inches plus 99-100%
Rough guess.
My tuber is 8 inches. I achieved this by growing in in my greenhouse with high humidity, NEVER letting the soil dry, high phosphate fertilizer and a treatment with Indole Acetic Acid plant growth hormone. My plant was about the size of a softball when I got it and weighed about two lbs. Now it weighs in at over 7lbs.
Its a beautiful thing :-)

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I forgot to mention that all this growth was achieved in only ONE season. While this kind of growth is not unheard of, it it rare. I grew it in a 35 gallon pot and when I unpotted it, it had filled every square inch of the soil with roots. All the soil came out in one lump and it had produced 15 offsets.