What each audience size costs
| Audience size | CPM, engagement | CPM, brand awareness | Cost per engagement, engagement objective | Accounts |
|---|---|---|---|---|
| Under 10,000 | $110.66 | $127.28 | $1.79 | 17 |
| 10,000 to 30,000 | $82.66 | $64.00 | $2.12 | 19 |
| 30,000 to 100,000 | $66.68 | $40.55 | $2.20 | 22 |
| 100,000+ | $104.77 | $29.46 | $1.89 | 16 |
Two different shapes here, and they matter.
Brand awareness falls monotonically, from $127.28 to $29.46. If you are buying reach, bigger is simply cheaper, all the way up.
Engagement does not. It bottoms at $66.68 in the 30,000 to 100,000 band and rises again to $104.77 above 100,000. If you are buying engagement, the mid-sized audience is the sweet spot and the biggest audience you can build is not.
Reach per $1,000
| Audience size | People reached per $1,000, brand awareness | People reached per $1,000, engagement |
|---|---|---|
| Under 10,000 | 7,720 | 7,542 |
| 10,000 to 30,000 | 12,248 | 8,711 |
| 30,000 to 100,000 | 21,117 | 11,656 |
| 100,000+ | 28,114 | 8,528 |
On brand awareness, $1,000 reaches 3.6x more people at 100,000+ than under 10,000. On engagement the same money peaks at 11,656 in the mid band and falls back. This is the clearest single argument for separating your reach campaigns from your engagement campaigns rather than running one audience for both.
How fast each size burns out
| Audience size | Median days to one full pass |
|---|---|
| Under 10,000 | 14 days |
| 10,000 to 30,000 | 32 days |
| 30,000 to 100,000 | 48 days |
| 100,000+ | 53 days |
A full pass means the average member has seen the ad once. It matters because fatigue tracks cumulative frequency rather than elapsed time: engagement is down 9% at one full pass and 22% at five, and landing page click rate falls faster, down 10% and then 35%.
So an audience under 10,000 reaches its first fatigue checkpoint in a fortnight, while an audience over 100,000 takes nearly two months, and only about one campaign in ten ever reaches a full pass at all. If you are rotating creative on a monthly calendar and running a 9,000-person audience, you are a fortnight late every time.
The warning sign is not cost per click. CPM falls as a creative fatigues, which hides the decay, so cost per click stays flat and warns you roughly a month late. Watch landing page click rate against cumulative frequency instead.
What it costs to reach half an audience
| Audience size | Cost to reach half of it |
|---|---|
| 3,400 | $448 |
| 9,800 | $1,752 |
| 27,000 | $3,544 |
| 81,000 | $9,740 |
| 260,000 | $15,832 |
Useful for planning, because it converts an abstract audience number into a budget. Note the shape: reaching half of 260,000 costs 1.6x what reaching half of 81,000 costs, for 3.2x the people. Large audiences are more efficient to penetrate, not less.
Size is really about budget pressure
Audience size is not independently magic. What it actually controls is how much money lands on each member, and that is what prices the auction:
| Spend per day per 1,000 members | Typical audience | CPM | Cost per landing page click |
|---|---|---|---|
| Under $0.50 | 130,000 | $39.57 | $8.07 |
| $1 to $2 | 26,000 | $78.10 | $16.19 |
| $5 to $10 | 5,000 | $121.81 | $22.00 |
A 5,000-person audience is not expensive because it is small. It is expensive because almost any sensible daily budget puts $5 to $10 a day against every thousand members in it. Build the audience to fit the budget you actually have.
How to pick a size
Reach and awareness: as large as your ICP honestly allows. 100,000+ at a $29.46 CPM and 28,114 people per $1,000.
Engagement and retargeting pool building: 30,000 to 100,000. Cheapest engagement CPM at $66.68 and the best engagement reach per $1,000.
Under 10,000: only with a small budget and a short flight. You will pay a $127.28 CPM and burn a full pass in a fortnight, so plan creative rotation at two weeks, not a month.
The arithmetic to run first: daily budget divided by audience size, times 1,000. Keep it under $2 and most of these problems do not arise.
All figures are from Kiin Labs: a panel of 1,071 B2B LinkedIn advertising accounts, $79M of spend, 22,942 campaigns, 1.34 billion impressions, 2.4 million landing page clicks and 139,231 form submissions, for the 12 months to 7 September 2026. LinkedIn Audience Network is excluded throughout. Figures are medians, not averages, because the top 10% of accounts spend 64% of the money. Where a comparison says "paired", both options ran inside the same account, so account quality cannot explain the gap.