Ad Auction Floor-Price Simulator

Scenario

Floor price (CPM)$2.00

Bids below this are rejected.

Bidders per impression2

How many demand sources bid on each impression.

Bid level (median CPM)$5.00

The typical bid.

Bid spreadσ 0.60

How far bids scatter around the median (lognormal σ).

Auction type

The winner pays the second-highest bid, or the floor if it is higher.

99.6%

Fill rate

impressions with a bid ≥ floor

7.0%

Bid-rejection rate

bids below the floor

$4.09

Avg clearing price

CPM on filled impressions

$4.07

RPM

per 1,000 impressions, unfilled = $0

Same 2,000 simulated impressions at every floor. In this scenario RPM peaks at $4.27 with a $4.00 floor (86.8% fill); your floor gives $4.07.

RPM, fill rate, and bid-rejection rate at each floor price in the current scenario
Floor (CPM)	RPM	Fill rate	Bid-rejection rate
$0.00	$4.02	100.0%	0.0%
$0.33	$4.02	100.0%	0.0%
$0.67	$4.02	100.0%	0.0%
$1.00	$4.02	100.0%	0.3%
$1.33	$4.03	100.0%	1.5%
$1.67	$4.04	99.9%	3.5%
$2.00	$4.07	99.6%	7.0%
$2.33	$4.11	98.9%	10.7%
$2.67	$4.15	97.6%	14.9%
$3.00	$4.20	95.9%	20.3%
$3.33	$4.24	93.3%	25.6%
$3.67	$4.26	90.2%	31.1%
$4.00	$4.27	86.8%	35.9%
$4.33	$4.25	82.7%	40.7%
$4.67	$4.23	78.5%	45.6%
$5.00	$4.14	73.4%	50.5%
$5.33	$4.09	69.3%	54.6%
$5.67	$4.02	65.1%	58.2%
$6.00	$3.94	61.2%	61.5%
$6.33	$3.83	57.0%	64.9%
$6.67	$3.70	52.8%	68.3%
$7.00	$3.61	49.5%	70.9%
$7.33	$3.47	45.6%	73.5%
$7.67	$3.37	42.6%	75.8%
$8.00	$3.23	39.4%	77.9%
$8.33	$3.07	36.0%	80.0%
$8.67	$2.93	33.1%	81.7%
$9.00	$2.80	30.6%	83.3%
$9.33	$2.66	28.1%	84.9%
$9.67	$2.51	25.7%	86.3%
$10.00	$2.37	23.4%	87.6%
$10.33	$2.24	21.4%	88.8%
$10.67	$2.09	19.4%	89.8%
$11.00	$2.01	18.1%	90.6%
$11.33	$1.91	16.8%	91.3%
$11.67	$1.78	15.2%	92.1%
$12.00	$1.65	13.7%	93.0%
$12.33	$1.57	12.7%	93.5%
$12.67	$1.47	11.6%	94.1%
$13.00	$1.40	10.8%	94.5%
$13.33	$1.27	9.5%	95.2%
$13.67	$1.17	8.5%	95.7%
$14.00	$1.15	8.2%	95.9%
$14.33	$1.11	7.7%	96.1%
$14.67	$1.04	7.1%	96.4%
$15.00	$0.99	6.6%	96.7%
$15.33	$0.93	6.0%	96.9%
$15.67	$0.90	5.7%	97.1%
$16.00	$0.86	5.3%	97.3%
$16.33	$0.81	5.0%	97.5%
$16.67	$0.81	4.9%	97.5%
$17.00	$0.78	4.6%	97.7%
$17.33	$0.73	4.2%	97.9%
$17.67	$0.71	4.0%	98.0%
$18.00	$0.66	3.6%	98.2%
$18.33	$0.59	3.2%	98.4%
$18.67	$0.56	3.0%	98.5%
$19.00	$0.56	2.9%	98.5%
$19.33	$0.53	2.8%	98.6%
$19.67	$0.53	2.7%	98.7%
$20.00	$0.52	2.6%	98.7%

How the model works

The simulator draws 2,000 impressions from a seeded random number generator, so the same settings always give the same result. Each impression gets the chosen number of bidders, and each bid is a CPM drawn from a lognormal distribution around the median bid, with the spread as its log-scale standard deviation. Every floor in the chart reuses the same draws, so differences come from the floor alone.

Bid-rejection rate = bids below the floor ÷ all bids.
Fill rate = impressions with at least one bid at or above the floor ÷ impressions.
Clearing price: first-price pays the highest bid; second-price pays the higher of the second-highest eligible bid and the floor, so a lone eligible bid pays the floor.
RPM = mean clearing CPM across all impressions, counting unfilled ones as $0.

Things worth trying: with one or two bidders in a second-price auction, the floor often sets the price, so a floor near the median bid adds revenue. With many bidders, competition sets the price and a high floor mostly costs fill. In a first-price auction where bids do not react to the floor, as here, any floor can only remove revenue: the winner already pays their full bid.

Real marketplaces add things this model leaves out on purpose: bid shading, advertiser budgets and pacing, floors that vary by inventory, and bidders who learn from the floor.