What metrics do you monitor in Google Ads, and which ones actually matter?

Separate the metrics that describe the business from those that only diagnose the account — conflating the two is the most common mistake.

Business metrics — what you are judged on:

• Conversions and conversion rate — is it producing outcomes?
• Cost per acquisition (CPA) — the key metric for lead generation.
• Return on ad spend (ROAS) — the key metric for e-commerce.
• Total conversion value and profit, where you can get it. ROAS on revenue can hide a loss if margins differ by product.

Diagnostic metrics — useful for finding the cause, not for reporting success:

• Impressions and impression share — reach, and how much you are missing to budget or to rank.
• CTR — ad relevance and copy strength.
• Average CPC — competitiveness and Quality Score effects.
• Search terms and Quality Score — relevance hygiene.

Note: The answer interviewers are hoping for is that CTR and impressions are not goals. A campaign can have an excellent CTR and lose money. Equally, be ready to say that a rising CPA is not automatically bad — if volume grew and the CPA is still under target, that is usually the right trade. Knowing which direction to push depends on whether the business is constrained by efficiency or by volume.