IBU numbers

[Steven]

is ther a rule of thumb for these numbers? What do the numbers really mean, the higher the number__________, and the lower the number means___________________. Please fill in the blanks, so I can try to get up to speed with some of you better brewers.

[slothrob]

1 IBU is 1 mg/L or 1 ppm of isohumulone, or isomerized hop alpha acid.
IBU is a measurement of bitterness and a bigger number means more bitter, while a smaller number means less bitter.

There are rules of thumb for the range of IBU's that work for a given style of beer.
An IPA is usually in the neighborhood of 1 IBU for each point of original gravity. A 1.060 OG IPA would have approximately 60 IBU's, for example.

[ColoradoBrewer]

Something to keep in mind concerning IBU numbers is that the number can vary greatly depending on which formula was used to calculate it. There are no fewer than six formulae and their results vary quite a bit. So a brewer needs to do a little experimentation and pick one that matches his perception of the bitterness he perceives in his brew and stick with it. The only way to know for sure the bitterness for a given beer is to have it analyzed in a lab.

[warthog]

is ther a rule of thumb for these numbers? What do the numbers really mean, the higher the number the more bitter, and the lower the number means less bitter. Please fill in the blanks, so I can try to get up to speed with some of you better brewers.

ibu means international bitterness unit.

if i got you correctly, you are asking a very basic question, so there's your answer.