Probably between 2 and 3 oz. But some FOs have a higher usage rate, and some have a lower. Check the vendor's website. ETA: 32 oz total or 32 oz oils?
Hi Allen....it really depends on the particular FO and its suggested usage rate for skin safety, so I would first check with the supplier of where you bought it. Most of the ones I use are safe up to 6% ppo or higher, but I usually use the least amount I can get away with and still have my soap smell good for a long time, which is usually 5% ppo, but some are so strong that I can go even lower (2% ppo). For what its worth, I never go over 6% ppo on the FOs that say I can if I want to. They tend to weep out of the soap when used much higher than that. IrishLass
Check this out: https://www.brambleberry.com/calculator?calcType=fragrance The BB calculator uses weight of oil + water, vs some (such as Majestic Mountain Sage www.thesage.com) that use just oil weight. I cheat a bit here - even if my FO isn't from BB, I'll use their calculator. For example, most vendors have a Dragon's Blood FO and I figure the components are close enough that I can use BB's calculator for it. If they don't have a match, I'll use something similar - Apple Pie FO and Apple Strudel FO are probably pretty similar. Ideally you look on the vendors website, but if it's a discontinued FO that info might not be available.