Hey Niranjan, Aniruddh is right. It's impossible for anyone to arrive at an estimate, as it is dependent on real-time auction at the time of you running the campaign & fighting for place in their newsfeeds. A crude way of doing it is to look at your average CPMs over a course of 3 months (Across campaigns you believe targeted the right folks & gave you decent results). Take the lowest and highest CPM, this becomes your cost range for your TG. Look at your audience size in the retargeting funnel & you should be able to arrive at an estimate. If the CPM range is $50-$100, and retargeting audience size is approx 10K, then you should be looking at spending $500-$1000 for a frequency of 1. Higher the frequency, multiply the cost. This by no means is standard way of arriving at a budget. For all you know even if you spend $1000 per day, you might not fully be able to reach your TG as it depends on them logging into the platform & you winning the auction. In this case, your campaign won't spend or the frequency will go up