Metrics & KPIs
What is Cost per purchase (CPP)?
Cost per purchase (CPP) is what you pay in ad spend for one completed purchase: ad spend divided by the number of purchases. On Meta it's the sharpest bottom-line efficiency metric for e-commerce — a specific form of CPA where the tracked action is a sale — and it ties directly to whether a campaign makes or loses money.
Formula
CPP = ad spend ÷ number of purchases
Example
Spend $600 and drive 40 purchases → CPP = 600 ÷ 40 = $15. If your average order value is $50 at a 40% margin ($20 profit per order), a $15 CPP leaves $5 profit per sale. Push CPP to $22 and you're now losing $2 on every order, even though the campaign still 'works'.
Why it matters
CPP is the number that decides scaling: as long as it stays below your profit per order, every extra purchase adds money, so it's the cleanest go/no-go signal for raising or cutting budget on an ad set. It also connects straight to ROAS — CPP and ROAS are two views of the same result (ROAS ≈ average order value ÷ CPP), so watching CPP against your margin catches unprofitable spend that a healthy-looking ROAS can hide.
How to use and improve it
Set your maximum acceptable CPP from your margin (profit per order), then pause ad sets that run above it and scale the ones comfortably below. Lower CPP by lifting the landing-page conversion rate, raising average order value, and improving creative-to-offer match rather than only chasing cheaper clicks. Geniusko's daily auto-optimisation watches CPP per ad set and flags spend drifting above your break-even.
Frequently asked questions
What's the difference between cost per purchase and CPA?
Cost per purchase is a specific CPA where the action is a completed sale. CPA is the broader term covering any target action — a lead, a signup, an add-to-cart — so every CPP is a CPA, but not every CPA is a CPP.
How are cost per purchase and ROAS related?
They describe the same result from two angles. Roughly, ROAS ≈ average order value ÷ cost per purchase — so a lower CPP at the same order value means a higher ROAS. CPP frames it as cost; ROAS frames it as return.
What is a good cost per purchase on Facebook?
A good CPP is any figure comfortably below your profit per order. Because that depends entirely on your price and margin, there's no universal benchmark — judge it against your own break-even, not an industry average.
Why is my cost per purchase rising over time?
Common causes are creative fatigue (frequency climbing, CTR falling), a saturating audience, seasonal CPM spikes, or a weakening landing-page conversion rate. Check whether the change is in delivery cost or in how well traffic converts.
Related
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