How do you calculate reverse CPM?

Reverse CPM uses CPM = (Cost ÷ Impressions) × 1,000.

What is the reverse CPM formula for cost?

Cost = (Impressions ÷ 1,000) × CPM.

What counts as an impression?

It depends on the platform: served vs viewable impressions can differ. Compare CPM only when the definition matches.

Why might reverse CPM look too high?

Invoice adjustments, under-delivery, or mixing impression definitions can inflate effective CPM.

Should I use a CPM range?

Yes. A range is more realistic when CPM varies across placements, geos, or time windows.

Is this Critical Path Method (CPM)?

No. This page uses CPM as cost per 1,000 impressions in advertising.

Reverse CPM, reconciliation, ranges

Reverse CPM Calculator

Back-calc CPM from cost and impressions or estimate cost from CPM. Add range checks and copy a clean summary—free, no signup.

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Impressions definition checklist

Reverse CPM is only meaningful when impressions are defined consistently. Confirm billing definitions before you compare.

Served impressions

Counted when an ad is delivered by the server, regardless of viewability.

Definition: served

Viewable impressions

Counted only when viewability standards are met (e.g., 50% pixels for 1s).

Definition: viewable

Billing adjustments

Make-goods, under-delivery, or bonuses can skew effective CPMs in invoices.

Check: billing rules

Calculator

Reverse-firstInstantCopy summary

Reverse CPM from cost and impressions, or estimate cost from CPM. Add range checks and copy a shareable summary.

Cost ($)

Impressions

CPM range (optional)

Use a range to flag when CPM is unusually high or low.

Result

12,50 $

CPM

Range check

No range set

Add a CPM range to get a status.

Summary

Copy this block into a brief, doc, or email.

Reverse CPM Calculator summary

Mode: CPM from cost
Cost ($): 2.500,00 $
Impressions: 200.000
CPM: 12,50 $

Formula:
CPM = (Cost ÷ Impressions) × 1,000

Assumptions: impressions may be served or viewable depending on billing; CPM can vary by placement, geo, and time window.

Formula

CPM = (Cost ÷ Impressions) × 1,000

AI insights (optional)OpenRouter

Interpret reverse CPM results with reconciliation tips and next-step checks. AI does not change the calculations.

Context (optional)

Avoid sharing sensitive data. Insights are advisory only.

References

Use these references to confirm CPM definitions and formulas.

Related calculators

Keep normalizing media metrics with these tools.

CPM Spend Calculator CPM to Impressions Calculator CPC to CPM Calculator

Why this reverse CPM calculator is different

Reverse-first flow

Start with cost + impressions to back-calc CPM for reconciliation.

Range signal

Add an expected CPM range and flag when your result drifts.

Copy-ready summary

Share inputs, outputs, and assumptions in a clean block.

Optional AI insights

Get interpretation and next-step checks without changing the math.

How it works

Pick a mode

Reverse CPM from cost + impressions or estimate cost from CPM + impressions.

Enter the known values

Provide cost and impressions (or CPM and impressions) to calculate the missing output.

Validate and share

Add a CPM range, note impression definitions, and copy the summary.

FAQ

Reconcile CPM in seconds

Back-calc CPM, sanity-check with ranges, and share the summary.

Start calculating

Estimates only. Reverse CPM is only meaningful when impression definitions and billing rules are consistent.