I've been using Advantage for many years now and I buy the large dog kind,over 55lbs, and then I measure it. I've been buying it from http://www.entirelypets.com/. They usually have a lot of summer specials and once you're on their e-mail list they'll e-mail you special with codes to save even more.

I bought the over 55lb dog advantage 12 month pack which is actually two 6 month packs for $114.99 and I also got 10% off of my order and free shipping since I spent over $85. I have 4 cats and this will last me for a long time. Each tube lasts me about 2 months or so I think.

For cats under 9lbs you give them 0.4ml and for cats over 9lbs you give them 0.8ml. I have one who is 9lbs so she gets 0.4ml and the other 3 get 0.8ml. I hope that this info has helped you. Good luck.