How much yeast to add for 1.5 gallon brew?

I am using a the typical vial of white labs English ale yeast and need to know how much to add for a 1.5-gallon batch. On the back of the vile it says the amount is for a 5-gallon batch.

A lot of fluid is in it, so should I shake it up for even disbursement and then eyeball about 33% of it?

Thanks

I'd check Mrmalty.com and go to the "pitching calculator". That will tell you exactly how much yeast would be optimum for the batch.

My first instinct is to say to use the whole thing. Sure, it says it's "pitchable" but for any beer over 1.040 (a 5 gallon batch) it's underpitching. A third of the yeast would probably not be adequate, but half might be ok. If you check mrmalty's pitching calculator, you could see for sure. Here's a link: http://www.mrmalty.com/calc/calc.html

I pitched about 1/5th of a vile each into 2 of my 0.75 gallon batches that were 1.052 OG.

I’d say pitching one third is good. If this is a really big brew, I would not pitch over half. Why waste good yeast.

Thanks for advice.

According the link you sent me, I need 0.7 (70%) of the vile. So, I am assuming the amount of yeast in a vile of White Labs Yeast I have is some standard amount. Thus, I should pour in a little over half.

Correct?

I say use half, then save the rest for the next 1.5 gallon batch.