For cats and dogs under 30 lbs, use mini bars:

For Dogs:
<15 lbs — 1/2 bar twice a day
15 – 30 lbs — 1 bar twice a day

For Cats:
1/4 to 1/2 bar twice a day

For dogs above 30 lbs, use large bars:

31 – 80 lbs — 1/4 bar twice a day
>81 lbs — 1/2 bar twice a day