Flat fee vs. percentage of ad spend
By Moisés · Updated October 2026
There are two common ways to pay someone to run your ads: a share of what you spend, or one flat monthly fee. The difference looks small on the first invoice. It grows with every dollar you add, and it changes what your media buyer gets paid for.
How each model works
- Percentage of ad spend: your fee is a share of your monthly budget. At 15%, $10,000 in spend means a $1,500 fee, and $20,000 means $3,000. Some agencies add a monthly minimum, and some lower the percentage as spend grows.
- Flat fee: one price a month, agreed upfront and set by the work: how many platforms and accounts. Spend $10,000 or $20,000, and the fee stays the same.
- Hybrids: a base fee plus a percentage above a certain budget, or a bonus tied to results. They mix the strengths and the problems of both.
The percentage model is old. For most of the last century, agencies were paid a 15% commission on the media they bought, and many still price that way.
What each model rewards
Under a percentage, your media buyer earns more when you spend more, whether or not the extra spend pays off. Most media buyers are honest. The point is where the incentive points: the advice "cut this budget, it isn't working" costs them money.
Under a flat fee, telling you to spend more or less doesn't change what your media buyer earns. The way to keep you as a client is to make your spend work.
The math at three budgets
Same work, same platforms. Only the fee model changes.
| Monthly ad spend | At 15% of spend | Flat fee of $400 |
|---|---|---|
| $5,000 | $750 | $400 |
| $10,000 | $1,500 | $400 |
| $20,000 | $3,000 | $400 |
At $20,000 a month, the gap is $2,600 a month, or $31,200 over a year. That money can go back into your ads.
When a percentage can make sense
A percentage isn't always the wrong deal. It can be fair when:
- the work really grows with the budget: many platforms, many markets, many campaigns;
- the agency also makes your creative, and more spend means more production;
- the fee has a cap, or the percentage drops as you spend more.
If that's you, ask for the cap in writing. If it isn't, a percentage mostly charges you for spending.
When a flat fee is the better deal
- You plan to grow your budget, and you don't want your fee to grow with it.
- You want budget advice you can trust both ways: "spend more" and "spend less".
- You make your own ads, or can, so you pay for strategy and management, not production.
A flat fee has one condition: the scope has to be clear. Ask what's included, how many platforms it covers, and what happens if you add one.
Six questions to ask before you sign
Whatever the model, ask these:
- Who owns the ad accounts, the pixel, and the data? It should be you.
- Is there a setup fee, and what does it pay for?
- Does the fee change when my spend changes?
- Who runs my account day to day: the person selling it to me, or someone else?
- How will I see results, and how often?
- What's the minimum term, and what happens when I leave?