Based on advice I was given on here and from my vets (when I panicked having given my kittens 3 x recommended dose of panacur paste) if in doubt always go a "size" up for the wormers. The reason why you have to weigh your pet carefully for wormers is so that you give them enough to kill the worms, not because the dose could be dangerous. I'm told it's very hard to overdose on wormers; the safety margin is enormous xxx hope that helps xxx
Saying that, I've been using diatomaceous earth as a wormer on the cats and dog and as far as I can tell it's done a sterling job