How much chlorine for a small vinyl pool of 150 gal?

To be on the safe side you really need a test kit, and before doing the chlorine you need to check the pH level as this will control your chlorine. The pH needs to be between 7.4 - 7.6 if it goes above 7.8 then the chlorine does not work very well.

chlorine needs to be higher than 1ppm but below 5ppm the desired amount will be dependent on your plans for the pool and how it is used eg dirty kids in - out in the mud back in again this will eat up chlorine, deodourants hair products cosmetics sweat etc etc anything that gets in the water will eat it up.

But when it comes to how much chlorine to put in it is easier to add a bit more than try and get it out (without buying more products eg. sodium thiOSulphate).

It will eventually become like adding sugar to a cup of coffee you get to know how much you need.