Dynamic Bids Down Only vs Fixed Bids: which one fits a Merch seller

For most Merch by Amazon campaigns, dynamic bids down only is the safer choice. Without a placement adjustment, your typed bid becomes the most Amazon will pay, and it may bid less on clicks that look unlikely to buy. Fixed bids pay your full bid in every auction, which buys cleaner data and sometimes more impressions, and dynamic bids up and down can double the bid.

On a royalty product that difference decides whether an order pays. With $3-5 kept per sale, a bid that is safe as typed can turn into a loss once Amazon is allowed to raise it.

This guide explains what each strategy does in Amazon's own words, how to work out the highest price any click can cost, and when a royalty seller should pick each one.

What the three bidding strategies do

Every Sponsored Products campaign has one bidding strategy, and it applies to every keyword and target inside it. Amazon's dynamic bidding guide describes them like this:

• Dynamic bids - down only: Amazon will "reduce your bids for impressions that are less likely to convert to a sale." It never raises them.
• Dynamic bids - up and down: Amazon will "increase or decrease your bids by up to 100% for all placements based on performance." Its example is a $1.00 bid that can reach $2.00.
• Fixed bids: Amazon uses your exact bid and doesn't adjust it for the likelihood of a sale.

Placement adjustments sit on top of all three. They raise the bid by a percentage you choose for top of search or product pages.

Amazon's Sponsored Products best practices guide says you "can add placement bid adjustments up to 900%". It also describes fixed bids as using "the exact bid you've entered".

One detail varies between Amazon's own pages. The dynamic bidding guide says up and down can raise bids by up to 100% for all placements, while the author's guide to Sponsored Products gives 100% for top of search and 50% elsewhere. For a cautious plan, assume the 100%.

The guide also asks advertisers using up and down to "be prepared to potentially spend double the amount of the bid you input." On a $20 shirt, that warning deserves more weight than it gets.

The number that matters: your worst-case bid

On a royalty product, the question isn't the bid you typed. It's the most any single click could cost under the campaign's settings, compared with the most a click is worth.

The most a click is worth is your break-even bid: royalty kept per order × conversion rate. The bid strategy guide works through it for five price points. For a $19.99 shirt keeping about $4.55 after returns (a worked example, not an Amazon figure) and converting at 8%, break-even is about $0.36.

Here is the worst case for a typed bid of $0.29, 80% of that break-even:

Amazon doesn't publish one formula for how a placement adjustment and an up-and-down raise combine. The last row assumes they stack, which is the safe way to plan a ceiling.

Without a placement adjustment, down only and fixed both stay under break-even. Up and down crosses it as soon as Amazon raises the bid by about a quarter.

The row people miss is the fourth one. A +50% top-of-search adjustment pushes even a down-only campaign past break-even on those clicks, because the adjustment raises the bid before Amazon's strategy has any say.

That doesn't mean every click costs the maximum. It means some of them can, and those are usually the clicks Amazon expects to convert best. You find out in the cost per click column, after the money is spent.

When dynamic bids down only fits

Down only suits most Merch campaigns, for three reasons.

Your bid stays the ceiling. If you set bids from break-even and add no placement adjustment, down only never bids above them. That makes the maths in the break-even ACoS table hold in practice, not only on paper. It trims weak clicks. Amazon lowers the bid where it predicts a low chance of a sale. On a thin royalty, paying less for those clicks matters more than winning every one of them. It's forgiving across hundreds of campaigns. A seller with 300 designs can't watch every auction. A strategy that can only lower bids limits the damage of a bid set a little too high.

The cost is reach. When Amazon lowers your bid in an auction, you may lose that auction. On keywords where your bid is already low, down only can leave a campaign with very few impressions.

When fixed bids make sense

Fixed bids pay your typed bid in every auction your ad enters. That has real uses:

• Clean tests. If you are comparing two bids or two keywords, fixed bids remove one moving part. The cost per click you see reflects the bid you set and the competition, not Amazon's adjustments.
• Very low bids that don't serve. A $0.15 bid on a launch-price design may win almost nothing once down only lowers it further. Fixed keeps the full $0.15 in play.
• Short, deliberate pushes. For a design you know converts, fixed bids can win a few more auctions in a peak week, with the bid still as the cap.

The risk is the opposite of up and down: you pay full price for clicks Amazon would have rated as weak. On a design that converts at 5%, those clicks are where most of the wasted spend sits.

A simple rule: use fixed bids where your bid is well under break-even and you want the traffic, and down only everywhere else.

When up and down can work for a royalty product

Up and down isn't always wrong. It works when even a doubled bid stays under break-even.

Work out break-even for the design: royalty kept × conversion rate. Use at least 30 clicks of data, or the conversion rate is mostly luck.

Halve it. That is the highest typed bid that stays safe if Amazon doubles it.

Add any placement adjustment to the worst case and check again.

Use it only on proven designs. Up and down spends more per click on the auctions Amazon likes. That only pays when the design has shown it converts.

For the $19.99 example, break-even is $0.36, so up and down is only safe at a typed bid of $0.18 or less, with no placement adjustment. For a $15.99 shirt keeping about $2.27 at 8% conversion, break-even is $0.18 and the safe up-and-down bid is $0.09, which rarely wins anything.

In practice that makes up and down a niche tool for higher-priced designs with strong conversion, not a default.

How to switch and judge the result

The bidding strategy is a campaign setting. You can change it in the campaign's settings in the console, or in the campaign rows of a bulk file if you edit many at once.

Pick one group of campaigns with similar designs and prices, so the comparison means something.

Note the starting numbers: clicks, cost per click, orders and spend for the last 14 days.

Change only the strategy. Leave bids and budgets alone, or you won't know which change did what.

Wait about two weeks. Amazon's guide suggests reviewing bids "about once every two weeks," and a Merch design needs that long to collect enough clicks.

Compare cost per click and orders, not just ACoS. If CPC rose but orders didn't, the switch cost money.

To check whether a cost per click still pays, the free Merch max bid calculator returns the break-even bid from your price, royalty and conversion rate.

How PPC Optimizer Pro handles this

Choosing a strategy is only half of it. The bids inside each campaign still have to sit under break-even, target by target.

PPC Optimizer Pro's Lab reads your 60-, 30- and 14-day bulk files plus your sales report. It works out each target's break-even bid from its royalty and its own conversion rate, with returns subtracted, and suggests bid changes that stay under it. Every change comes with its reason, and you download one Amazon-ready bulk file to upload.

There is a 7-day free trial, and the free tools at /free-tools work without an account.

FAQ

What does dynamic bids down only mean on Amazon?

Amazon may lower your bid in real time for clicks it thinks are less likely to lead to a sale, and it never raises it. Without a placement adjustment, your typed bid is the most you pay for a click.

Is fixed bidding better than dynamic bids down only?

Neither is better everywhere. Fixed bids give cleaner test data and can win more auctions at a low bid; down only spends less on weak clicks. For most royalty products, down only is the safer default and fixed suits tests and very low bids.

Can dynamic bids up and down make me lose money?

Yes, if your typed bid is above half of your break-even bid. Amazon can raise it by up to 100%, so a bid that pays as typed can cost more than an order earns in the auctions where it's doubled.

Do placement adjustments work with down only?

Yes. Amazon lets you add placement adjustments under any bidding strategy, and they raise the bid for that placement. A +50% top-of-search adjustment on a down-only campaign can lift a $0.29 bid to about $0.44, so count it in your worst-case bid.

How long should I test a bidding strategy?

About two weeks, which matches Amazon's suggestion for reviewing bids. Change only the strategy during that time so you can tell what it did.

Keep reading

• Amazon PPC Bid Strategy for Merch: how much to bid at each price
• Break Even ACoS for Merch by Amazon: the table for 5 price points
• How to lower Amazon PPC costs