Flat fee vs percentage of ad spend: when each costs less

Picture two agency quotes on your desk for the same Google and Meta ads work. One asks for 15% of your monthly ad spend, the other for a flat $2,000 a month (both hypothetical). The cheaper one comes down to a single number you can work out in a minute. Below you'll find it, plus the contract terms that matter as much as the rate.

Corren charges a flat monthly fee for ads management, never a percentage of ad spend (how our flat-fee pricing works), so we have a stake in this question.

How the two pricing models work

Percentage of ad spend

A percentage fee ties the agency's pay to what you spend on ads. WebFX and AgencyAnalytics both put typical fees at 10% to 20%, and Semrush quotes a wider 10% to 30%. WebFX says fees usually fall as total spend rises.

Many percentage deals add a floor. WebFX's Pro plan, for example, charges $975 or 15% of spend, whichever is higher, for budgets of $5,000 to $30,000.

Flat monthly fee

A flat fee is priced on the work: the campaigns and channels, the creative, the reporting, and any landing page changes. Published ranges vary widely:

• From around $500 a month for smaller Google Ads budgets (AgencyAnalytics)
• $1,000 to $3,000 a month (WebFX), though its own entry-level plan is a flat $750
• $1,500 to $3,000 a month for small local businesses (Semrush)
• $2,500 to $10,000 a month, according to Navah Hopkins' Ask a PPC column in Search Engine Journal

Every range here comes from an agency, a software vendor, a directory, or a columnist, not an independent survey, so treat any claim of "the industry standard" with care.

The break-even formula

Break-even monthly ad spend = flat fee divided by percentage rate.

Below that spend, a percentage fee with no minimum costs less. Above it, the flat fee costs less, as long as both quotes cover the same work.

Take the two hypothetical quotes from the top. $2,000 divided by 0.15 is about $13,333, so that's the monthly spend where the two cost the same. Against a 10% rate the same fee breaks even at $20,000, and against 20% at $10,000.

What the two quotes cost at five budgets

At 15% with no minimum, against hypothetical flat fees (none of them a Corren price or any agency's quote):

• $1,000 a month: $150 against $2,000, so the percentage costs $1,850 less
• $5,000 a month: $750 against $2,000, so the percentage costs $1,250 less
• $15,000 a month: $2,250 against $2,000, so the flat fee costs $250 less, or $3,000 a year
• $30,000 a month: $4,500 against $2,000 to $3,000, so the flat fee costs $1,500 to $2,500 less
• $60,000 a month: $9,000 against $6,000, so the flat fee costs $3,000 less

Flat fees rise with the work, so the two largest budgets carry higher flat quotes, and a bigger quote should name the extra work it covers. Run the formula with all-in numbers: use the minimum fee at low spend, and add any separately billed creative, landing page, or tracking work.

When a percentage fee costs less

• Small budgets with no minimum. At $3,000 a month, 15% is $450, below the roughly $500 starting point AgencyAnalytics gives for flat Google Ads fees.
• Seasonal businesses. If spend falls from $10,000 to $4,000 in the off-season, a 15% fee drops from $1,500 to $600. A flat fee doesn't.
• Short tests. A two- or three-month trial at modest spend can cost less on a percentage, if there's no long minimum term or large setup fee.
• A percentage with a dollar cap. If an agency caps its fee at a fixed amount, you keep the low-spend advantage without the high-spend cost.

At very small budgets, the floor sets the price, not the rate. AgencyAnalytics reports median monthly spend of $1,024.79 on Google Ads and $784.33 on Meta among more than 7,000 of its users as of January 2025. At $1,000 a month, WebFX's flat $750 plan equals 75% of spend, and a $975 minimum equals 97.5%.

When a flat fee costs less

• Spend well above break-even. At 15%, each extra $1,000 of monthly spend adds $150 to the percentage fee and nothing to a flat fee with the same scope.
• Budgets you expect to grow. Tripling spend triples a percentage fee. A flat fee changes only when the work does.
• Several channels under one team. A percentage applies to combined spend. Hypothetically, $8,000 on Google plus $6,000 on Meta is $14,000, and 15% of that is $2,100, more than a $2,000 flat fee covering both.

If one team would run both your Google Ads and Facebook and Instagram ads, compare quotes on both channels together.

What each model rewards

• Percentage of spend. The agency earns more when you spend more, and cutting wasted spend cuts its own fee. Hopkins writes that percentage pricing "doesn't always align the management fee with the client's well-being," though the fee does fall on its own in slow months.
• Flat fee. The agency earns the same at $3,000 or $30,000 of spend, so its pay doesn't depend on its budget advice. The risk is less work for the same money, so get a written scope covering campaign reviews, new ad tests, and reports.
• Performance-based. Paying per lead or sale looks aligned, but it depends on what counts as a conversion and who controls the tracking. Hopkins notes it "often means the agency retains account ownership."

Larger accounts can need more campaigns, creative, and new landing pages. In our view, that work grows with scope, not with each extra dollar of budget.

Contract terms to check before you sign

• Minimums. Above $30,000 a month, WebFX charges "$4,500 or 12% of ad spend, whichever is greater," so the $4,500 minimum applies until spend passes $37,500.
• Contract length. Semrush advises avoiding agencies "that require long-term commitments without a performance-based exit clause." In Credo's survey, last updated in June 2022, 30.52% of PPC providers had a 6 to 12 month minimum and 26.3% had none.
• Setup fees. WebFX's first-month charges run from $1,200 to $5,800, depending on the plan. Ask what the setup fee produces and whether you keep that work if you leave.
• Add-ons. Semrush notes that some agencies charge extra for copy, design, and video, and that conversion rate optimization may be billed separately. A low fee plus add-ons can cost more than an all-in quote.
• Google account ownership. Only Admin users can grant access and unlink an agency's manager account. Anyone with Admin access can end that link at any time, but only if someone at your business holds that login.
• Meta ownership. Jon Loomer recommends that the client own the business portfolio and every asset in it, with the agency added as a partner you can remove.
• Fee transparency. Under Google's transparency requirements, an agency that charges a management fee must disclose it in writing before the first purchase and show it on every invoice. Where you can, have Google and Meta bill your own payment method directly.

Questions to ask before signing

Ask every agency the same questions so the answers line up. If you want a baseline first, our free recorded audit reviews your ads, landing pages, and tracking, and you can take it to any agency.

1. What is my all-in monthly fee at half my current spend, at my current spend, and at double it?
2. Is there a minimum fee or a "whichever is higher" clause?
3. What does the fee include, and what is billed separately?
4. How long is the contract, what is the notice period, and is there a cancellation fee?
5. Will my ad accounts, landing pages, and tracking stay in my name, with someone at my business holding Admin access?
6. How will you decide whether I should spend more or less, and does that change what I pay you?

Where Corren stands

Corren is a studio run by its two founders, Aaron and Jerry. We charge a flat monthly fee, month to month, set by the work involved and never by your ad spend. At small budgets, a percentage deal with no minimum can cost less than a flat fee, ours included.

Compare quotes in dollars at your real spend and get the scope in writing. If you'd like a second opinion first, send your website for a free audit.