"What should I charge?" has an actual formula: engaged readers × your niche's CPM × the slot type. This runs it with current 2026 CPM ranges, so your first sponsor quote is defensible rather than hopeful. Runs in your browser, no signup.
CPM ranges reflect 2026 sponsorship-market guides; sponsorship is a negotiation, not a price list — treat this as your anchor, not a ceiling. Under ~10,000 engaged readers, quoting a flat rate (from this range) usually sells better than talking CPMs. Rates in USD because that's how the sponsorship market quotes; convert for UK sponsors at the day's rate.