CAC and ROAS without the jargon wall

CAC (customer acquisition cost) is what you pay for a new customer. ROAS (return on ad spend) is revenue divided by ad spend on-platform. They answer different questions - do not optimize both blindly.

Targets by model

Subscription SaaS: CAC payback under 12 months is a common bar. DTC: contribution margin after COGS must exceed CAC on first order or LTV must carry repeat. Know your margin before you chase 4× ROAS screenshots.

When to scale

Scale when MER is stable for 2–3 weeks and fulfillment can handle volume. Increase budget 15–25% increments; watch new-customer CPA, not just ROAS spikes from retargeting.