I love the butterfly koi and plan to dig a new pond this spring. How many fish in say a eiht foot pond or manybe a even a eighteen foot by say six foot one. I read some where about how many fish to a square foot.

It depends on a lot of factors but from what i have read 100 gallons per koi is the minimum while growing and 200 is the bare minimum when mature (with 1000 each much better).

Luke is right! Koi are messy creatures, and can grow 6-7 inches in a YEAR! So, they need lots of space, but there is nothing more rewarding than to see your big huge koi swimming up to you and taking food out of your hand....I have 5 koi left in a 1300 gl pond, and they grow like weed....

Can you tellhow many ft. to an 100 gal. or how many can I put in a 16x8 ft. pond. I am planning on butterfly koi. I think they need more or do they?

I would suggest you ask those questions too a member of a local koi club. There is so much that goes into building a proper koi pond it will make your head spin and by getting info from somebody that lives in your climate will only help. I am pretty sure with just a phone call someone will be more than happy too help you. If kept in proper conditions koi will get HUGE!!! My only advice as of now is once you figure how deep you can make your pond add another foot of depth.
If you check out the thread I started about my pond, I posted a picture of a real nice 4" longfin ginrin yamabuki I got for $25.

I have 750 gallons which will be too small by next year and some of my Koi will be going to a friends pond. They were only 2 inches when I got them this spring and are now between 5 and 8. Once they reach 12 inches some may need to be moved. Right now they are fine. They do grow extremely fast.

I got a koi once for 15 $ it died the next day i
was kinda mad and i brought back the fish to the
pet shop ..... i think they don't like me any more
*the pet shop owner*

but my goldfish was takeing care of
it when she was dieing it was sad