The usual way to set an Amazon PPC budget is to pick a round number that feels safe, run it for a month, and then either cut it because ACoS looks high or raise it because sales looked thin. Neither decision is based on much. The budget was never connected to what the business needed from ads.

This guide builds a budget you can defend: from margin, from a sales goal, and from what clicks cost in your category. Then it covers how to split it across campaigns, how daily and portfolio caps fit together, and which signals should make you change it.

Start with what you can afford per sale

Before any total, work out the most you can spend on ads to win one sale. That is your break-even ACoS: margin before ad spend, as a share of the sale price. If a product sells for 40 and leaves 12 after product cost, Amazon fees and fulfillment, the break-even ACoS is 30 percent. Spend more than that per sale and each ad-driven unit loses money.

Your working target usually sits below break-even, to leave profit, or occasionally above it on purpose during a launch, when you are buying rank and reviews. What a good ACoS is covers how to choose between the two.

Build the total from the goal

Now work forward from what you want ads to produce. An illustrative example for Sunhollow Supply:

Goal: 6,000 in ad-attributed sales next month at an average order value of 30. That is 200 orders.

Expected conversion rate from ad clicks, taken from their own last 60 days: 10 percent. So 200 orders need about 2,000 clicks.

Average cost per click in their campaigns: 0.80. So 2,000 clicks cost about 1,600.

That gives an ACoS of about 27 percent. If their target is 30 percent, the budget fits. If their target were 20 percent, the plan would need a higher conversion rate, lower click costs, or a smaller goal. The arithmetic tells you which lever is out of line before you spend anything.

Use your own numbers. If you have no history, start smaller, run for three to four weeks, and rebuild the plan from real data. How CPC works covers why click costs vary so much by keyword.

Split it across campaigns by job

A total budget does nothing until it is divided. Split by what each campaign is for, not evenly.

Proven performers, usually exact match campaigns on keywords that already convert, get the largest share, because they turn budget into sales most reliably.

Discovery campaigns, auto and broad, get a smaller fixed share. They find new search terms but convert less predictably.

Brand defense on your own brand terms gets enough to hold the top of the results, which is usually cheap.

Tests and launches get a ring-fenced amount with a clear end date, so they do not quietly absorb money meant for proven campaigns.

Write the split down. Revisit it monthly, moving budget from campaigns that underperform their share to campaigns that are capped and converting.

Daily budgets and the out-of-budget problem

Amazon campaign budgets are daily. Amazon may spend more than the daily budget on a given day while keeping the month's spend in line with it, so treat the daily figure as an average rather than a hard wall.

The larger risk is running out early. A campaign that exhausts its budget at two in the afternoon sits dark through the evening, which in many categories is when shoppers convert best. Check the budget status column regularly. If a strong campaign runs out every day, it needs either more budget or less spend in its weaker hours. Running out of budget covers how to tell which.

Portfolios as a ceiling

Portfolios let you group campaigns and set a budget cap for the group, either as a monthly recurring cap or for a date range. That cap sits above the campaign budgets. It is useful for keeping a product line, a brand or a client within a fixed amount, and for protecting against several campaigns spiking at once.

A sensible setup is daily campaign budgets doing the routing and a portfolio cap acting as a safety ceiling you rarely hit. If you hit the cap often, the campaign budgets underneath are set too high for the plan.

One more check before you commit: compare the plan to last year's same month if you have it. Seasonal categories can need a very different budget in a peak month than in a quiet one, and a plan built from a quiet month will run out early when demand rises.

When to change the budget

Change a budget for a reason you can name. Good reasons: a campaign is capped every day at an ACoS under target; a campaign is spending its full budget at an ACoS well above target; stock is about to run short; a seasonal peak or promotion is coming; margin changed because of a price or cost change.

Bad reasons: one bad day, one good day, or a vague feeling that spend is high. Give changes at least a week to show their effect before changing again. Budget pacing covers how to watch spend through the month without overreacting.

Frequently asked questions

How much should I spend on Amazon PPC per month?

There is no fixed figure that fits every seller. Work it out from your goal: the ad sales you want, divided by the conversion rate you expect, gives clicks; clicks times your average cost per click gives spend. Then check that spend against what your margin allows at your target ACoS.

Should I set Amazon budgets at the campaign level or use a portfolio cap?

Use both. Campaign daily budgets control where money goes day to day. A portfolio budget cap puts a ceiling on a group of campaigns over a period, which protects against several campaigns overspending together. Neither replaces the other.

What happens if my Amazon campaign runs out of budget?

The campaign stops serving for the rest of the day and starts again when the new day begins. If that happens before your best-converting hours, you miss your strongest sales. Either raise the budget on that campaign or shift spend away from weaker hours so the budget lasts.

Off Hours budget rules raise, lower and cap campaign budgets on the days and hours you choose, checked every 15 minutes. Start a free 14-day trial.