Open any ad dashboard and you'll meet a wall of acronyms. The good news: you only need to truly understand a handful. Here they are in plain English — what each one means, what "good" looks like, and the one number that quietly outranks them all.
Impressions
An impression is one ad view — a single time your ad was shown to one person. It's the rawest count there is. Impressions tell you about reach and volume, but on their own they say nothing about quality: a million impressions nobody noticed is a million wasted. Useful as a denominator, dangerous as a goal.
CPM and eCPM
CPM means "cost per mille" — the cost for one thousand impressions. A $2 CPM means you pay $2 every time your ad is shown 1,000 times. It's how ad space is usually priced.
eCPM is the "effective" version — what you actually ended up paying per thousand impressions across a whole campaign, blending every price you won at. It's the honest, all-in number. Watch eCPM to understand what your media is really costing.
eCPM = (total spend ÷ total impressions) × 1,000. So $50 spent on 25,000 impressions is a $2.00 eCPM.
CTR (click-through rate)
CTR is the share of impressions that got clicked: clicks ÷ impressions. A 0.6% CTR means 6 clicks per 1,000 views. It's a handy signal of whether your creative and targeting are landing — but treat it as a hint, not a verdict. A high CTR with no sales behind it is just expensive curiosity.
Putting them together
No single metric tells the story; the relationships do. Impressions show reach. eCPM shows what reach cost. CTR shows whether it resonated. Read them as a set: rising impressions with a steady eCPM and a healthy CTR is a campaign doing its job efficiently.
The metric that beats them all
Here's the one to anchor on: cost per result — what you paid for the thing you actually want (a sale, a sign-up, a visit). Impressions, eCPM and CTR are means to that end. If your cost per result is going down while you hold quality, the rest is detail. A good platform optimises toward that, not toward vanity clicks.
That's the philosophy behind adZoic's dashboard and reporting: every metric live, with AI-written summaries that tell you what moved and why. Curious how bids get priced in the first place? Read how ML values an impression.