Your Ads Manager dashboard says reach is up. Engagement's up. Maybe even your cost per result looks fine on paper. And yet — the phone isn't ringing any more than before, and you're left wondering whether your Facebook ads spend is actually doing anything.
That disconnect is common, and it's rarely because the numbers in Ads Manager are wrong. It's because the metrics platforms surface by default — reach, engagement, even cost per result — don't automatically answer the question you actually care about: is a new customer worth more than what it cost to get them?
This guide covers how to check Facebook ads ROI (Meta now runs both Facebook and Instagram through the same Ads Manager, so this applies to either) using reports you already have, and how to calculate the true cost per customer once your agency fee is folded in. If you split spend between Google and Meta, the same math applies to Google Ads too.
Why Meta's "Cost Per Result" Doesn't Settle It Either
Meta's own cost per result metric divides your ad spend by the number of results (purchases, leads, calls — whatever your campaign is optimized for). It's a legitimate number, and it's more useful than reach or engagement alone. But two things routinely sit outside it:
- Any management fee you pay on top of ad spend. If an agency runs your account for a flat monthly fee, Ads Manager has no way to know that — it only sees what Meta itself charged.
- What a customer is actually worth to your business. A $35 cost per result is meaningless on its own. It's either a great deal or a loss depending entirely on your margin per customer.
Ads Manager shows
Cost per result
ad spend only, no fee included
What you need to know
Blended cost
ad spend + agency fee, per customer
Neither number is fake or manipulated — they're just answering a narrower question than "did this make me money."
How to Calculate Your True Cost Per Customer on Facebook Ads
Same math as any other ad channel, just pulled from Ads Manager instead of Google Ads.
Step 1: Total your spend for the month.
Ad spend (from Ads Manager) plus any management fee your agency bills separately.
Step 2: Pull your total results.
Whatever counts as a new customer for your business — leads, bookings, purchases, calls.
Step 3: Divide total spend by total results.
This is your true, blended cost per customer.
Step 4: Compare it to what a customer is actually worth.
If you don't track this precisely, a conservative average sale value works fine as a starting point.
If that number is close to or above what a customer is worth, the campaign isn't working yet — regardless of how healthy reach or CTR look. If it's comfortably below, there's usually room to scale spend rather than cut it.
Facebook-Specific Things Worth Checking
- Placement mix. Facebook feed, Instagram feed, Stories, and Reels can have very different costs per result within the same campaign — a single blended number can hide one placement quietly underperforming.
- Attribution window changes. Meta's attribution windows have shifted more than once in recent years, which can make month-to-month "results" comparisons misleading if the counting method changed underneath you.
- Learning phase churn. A campaign that's frequently edited never exits Meta's learning phase, which tends to inflate cost per result independent of whether the offer itself works.
None of these mean the platform is broken — they're just reasons the same dollar amount can produce different real-world results month to month, which is exactly why the blended true-cost calculation matters more than any single Ads Manager metric.
Frequently Asked Questions
What's a good cost per result for Facebook ads?
It depends heavily on industry and what you're optimizing for — leads, purchases, or calls all price differently, and benchmark data shows costs vary widely by vertical — from under $30 in some categories to nearly $50 in others. There's no single "good" number; what matters is whether your blended cost per customer sits comfortably below what that customer is worth to you.
Is Facebook or Google Ads cheaper?
Neither is universally cheaper — they tend to serve different intent. Google Ads generally captures people actively searching for a solution, while Facebook/Instagram ads reach people who aren't searching yet. Comparing true cost per customer on each, using your own numbers, is more useful than a general "which platform is cheaper" answer.
Why is my cost per result going up over time?
Common causes include ad fatigue (the same audience seeing the same creative too often), rising competition in the auction for your audience, or frequent campaign edits resetting the learning phase. Refreshing creative and limiting how often you edit live campaigns both tend to help.
Should I judge performance by reach, engagement, or results?
Results. Reach and engagement show whether people are seeing and interacting with your ad, but only results (and what those results actually cost you, blended) tell you whether the campaign is making or losing money.
Do I need a separate calculation for Instagram ads?
No — Meta runs Facebook and Instagram ads through the same Ads Manager and often the same campaign, so the blended true-cost-per-customer calculation works identically regardless of which placements are running.
The Bottom Line
"Is my Facebook ads spend working?" isn't answered by reach, engagement, or even Meta's own cost per result metric in isolation. It's answered by one number: what a new customer actually costs you — ad spend plus any management fee — compared against what that customer is worth.
You can work this out yourself in a few minutes from your Ads Manager report and agency invoice, or run both through an audit tool that does the math automatically. Your first audit is free; audit packs are available after that with no subscription.
What does your true cost per customer look like once the management fee is added back in?