Passive income = your invested capital × annual yield. $100,000 at 5% = $5,000/year, or about $417/month, before tax.
At a 5% yield you'd need about $720,000. At 8%, about $450,000. The calculator shows your exact number above.
Money-market / high-yield savings ~4–5%, dividend stocks ~3–4%, index funds ~7% long-term average. Use what's realistic for you.