Floor Prices Explained: When to Raise, Lower or Let Them Work

A floor price (also called a price floor or reserve price) is the minimum amount you are willing to accept for an ad impression, usually expressed as a CPM: the price per 1,000 impressions. Any bid below the floor is rejected, even if it is the only bid.

Floors are one of the few levers a publisher can pull directly to change what their traffic earns. Used well, they stop your inventory from being sold too cheaply. Used badly, they leave ad slots empty and quietly cut your revenue. This guide explains how floor prices work and how to set them with confidence.

How a floor price works in the auction

In a modern ad auction, several buyers bid for the same impression at the same moment. The highest bid wins. A floor adds one rule: the winning bid must also be at or above the floor.

The second row is the key point. A floor never makes buyers pay more than they bid. It only decides which bids you refuse. If the floor is above what buyers are willing to pay, the impression earns nothing at all.

New to auctions? Start with what ad mediation is and header bidding vs waterfall.

The trade-off: eCPM versus fill rate

Raising a floor almost always does two things at once:

• eCPM goes up, because the cheapest impressions are no longer sold.
• Fill rate goes down, because some impressions find no bid above the floor.

What matters is the combination, which shows up in RPM and total revenue. A floor is working when total revenue for the unit rises. If eCPM climbs but revenue falls, the floor is too high. Our guide to eCPM, RPM and fill rate explains how these numbers connect.

How to set your first floor prices

1. Start with no floor. Let each unit run for one to two weeks so you can see what it naturally earns.
2. Read each unit's eCPM and fill rate. Note the typical eCPM for each unit, not just the site average.
3. Set a low first floor, well below the unit's typical eCPM. The goal is to remove only the very cheapest bids.
4. Wait and compare. Give the change several days with similar traffic, then compare revenue and fill rate with the period before.
5. Adjust in small steps. If revenue rose and fill held up, you can try a little higher. If fill fell sharply, step back.

When to raise your floor

• Fill rate is consistently very high and many winning bids are far above your current floor.
• Demand is seasonally strong, such as the run-up to the holidays (see Q4 ad rates).
• The unit is in a highly viewable position that buyers value; see viewability and refresh.

When to lower or remove your floor

• Fill rate dropped after you set or raised the floor.
• The unit often shows blank space.
• Demand is seasonally weak, for example in January.
• The unit is a video or specialised format with more selective demand; see video ads.
• A large share of your traffic comes from countries where bids are naturally lower; see eCPM by country.

Common floor price mistakes

• Copying a number from a forum. Another site's floor tells you nothing about your traffic.
• One floor for everything. Different units, devices and countries deserve different floors.
• Judging by eCPM alone. A higher eCPM with lower total revenue is a loss.
• Changing too much at once. Change one unit at a time so you know what caused the result.
• Set and forget. Demand moves with seasons and traffic. Review floors regularly.

A worked example

Imagine an in-content unit that, over two weeks without a floor, earned an average eCPM of $1.20 with a fill rate of 92%. Most winning bids were between $0.70 and $2.00, with a small share of very cheap bids around $0.15.

• First test: a floor of $0.30. Only the cheapest bids are removed. Fill drops slightly, eCPM rises a little and total revenue rises. Keep it.
• Second test: a floor of $0.60. Fill drops further, but most of the lost impressions were low-value. Revenue is about the same as the first test. This is close to the sweet spot.
• Third test: a floor of $1.10. eCPM looks impressive, but fill falls sharply and total revenue drops. Step back to the previous level.

The numbers here are only an illustration; your units will behave differently. The method is what matters: small steps, one unit at a time, judged by total revenue.

Floors by device, format and country

Demand is not the same everywhere on your site. Typical patterns publishers see:

Static floors vs dynamic floors

A static floor is a fixed number you set and change by hand. A dynamic floor is adjusted automatically, based on how bids for that unit have behaved recently. Dynamic floors can react faster to seasonal and daily changes, but they still follow the same principle: protect price without starving fill.

Floor prices in Advorex Media

In your Advorex Media dashboard, every ad unit has an optional Price Floor field: the minimum CPM a bid must clear to win that unit's auction. Leave it at 0.00 and the highest bid always wins, which is the right starting point for a new unit. Once you can see what a unit normally earns, you can add a floor and watch the effect in your reports. Units with a floor show a small "Floor" badge so you can see at a glance which ones are protected.

Key takeaways

• A floor price is the minimum CPM you accept; bids below it are rejected.
• Floors raise eCPM but lower fill rate. Judge them by total revenue.
• Start with no floor, learn what each unit earns, then test small floors.
• Raise floors in strong seasons, lower them when fill drops or demand is weak.