600mg of boric acid powder is about 1/3 to 1/2 of a number 1 size vegetable capsule. It’s not much, and don’t worry too much about being exact – just don’t overdo it. To get 600mg, you can empty out another capsule you have of a vitamin or something, and then using a really small spoon or tool, load in some of the boric acid each time.Buying boric acid already in capsules – don’t spend a lot on boric acid capsules, as this is a cheap product.