Prebid Price Granularity Calculator
How many line items does your header bidding setup need? This free Prebid price granularity calculator counts the price buckets for every preset or your own custom ranges, shows how a bid is rounded, and gives you the config to paste into Prebid.js.
Price granularity
Your setup
Line items needed
Prebid rounds every bid down to its bucket before sending it to the ad server, so a $1.87 bid in $0.10 steps competes as $1.80. Finer buckets compete more accurately but need more line items.
Prebid config
Prebid’s price granularity presets
| Preset | Steps | Price buckets |
|---|---|---|
| Low | $0.50 up to $5 | 10 |
| Medium (default) | $0.10 up to $20 | 200 |
| High | $0.01 up to $20 | 2,000 |
| Auto | $0.05 up to $5, $0.10 up to $10, $0.50 up to $20 | 170 |
| Dense | $0.01 up to $3, $0.05 up to $8, $0.50 up to $20 | 424 |
Definitions from the Prebid.js setConfig documentation. Bids above the top of the range are capped, so a $25 bid with the medium preset is sent as $20.
How to choose
- Most bids are low. Use small steps where most of your bids land, usually under $3 to $5, and bigger steps above that.
- Fewer line items are easier to manage. Each extra bucket is another line item to create and maintain.
- Per-bidder keys multiply line items. Only use them if you need bidder-level reporting or deals in the ad server.
- Match the currency. If you set floors or report in another currency, use the Prebid currency module so buckets line up.
New to Prebid? Read the Prebid.js setup guide, set the right timeout and see how Prebid has changed.
Frequently asked questions
What is price granularity in Prebid?
Price granularity decides how Prebid rounds bids before sending them to the ad server. A $1.87 bid becomes $1.80 with $0.10 steps or $1.85 with $0.05 steps. Each rounded price needs a matching line item in Google Ad Manager.
Which price granularity should I use?
Medium ($0.10 steps up to $20) is Prebid’s default and a good start. Dense or a custom setup gives more accuracy at low prices, where most bids are, without creating thousands of line items for rare high bids.
How many line items do I need for header bidding?
One per price bucket. Medium needs 200, dense needs 424. If you send separate keys per bidder, multiply by the number of bidders.
Why does Google Ad Manager limit line items?
An order can hold up to 450 line items, so large setups are split across several orders. Google Ad Manager’s built-in header bidding trafficking can also manage this for you.
Does rounding lose money?
The winning bidder still pays its full price, but the rounded price is what competes against Google’s own demand in the ad server. Coarse buckets can make a bid lose to a slightly lower AdX bid.