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Ad Metrics Calculator (CPM, CPC, CTR, CPA)

Computes the standard paid-advertising metrics cost per mille (CPM), cost per click (CPC), click-through rate (CTR), cost per acquisition (CPA) and click-to-conversion rate from campaign spend, impressions, clicks and conversions.

When to use

You have raw campaign totals (spend, impressions, clicks, optionally conversions) and need CPM, CPC, CTR, CPA or conversion rate, e.g. to compare channels or report performance.

Do not use when: You need revenue-based efficiency (use roas), publisher-side earnings from RPM (use ad-revenue), or conversion rate from site visitors rather than ad clicks (use conversion-rate).

Formula

CPM = spend / impressions × 1000; CPC = spend / clicks; CTR % = clicks / impressions × 100; CPA = spend / conversions; conversion rate % = conversions / clicks × 100

Inputs

Parameter	Type	Required	Description
`spend`	number	yes	Total amount spent on the campaign (any currency; outputs use the same currency). Range: ≥ 0, ≤ 1000000000000
`impressions`	integer	yes	Number of times the ad was shown. Range: > 0, ≤ 10000000000000
`clicks`	integer	yes	Number of clicks on the ad. Range: ≥ 0, ≤ 1000000000000
`conversions`	integer	no	Optional number of conversions (purchases, sign-ups) attributed to the campaign; enables CPA and conversion rate. Range: ≥ 0, ≤ 1000000000000

Outputs

Output	Type	Unit	Description
`cpm`	number		spend / impressions × 1000.
`cpc`	number		spend / clicks (absent when clicks = 0).
`ctr_percent`	number	%	clicks / impressions × 100.
`cpa`	number		spend / conversions (only when conversions > 0).
`conversion_rate_percent`	number	%	conversions / clicks × 100 (only when conversions given and clicks > 0).
`conversions_per_1000_impressions`	number		conversions / impressions × 1000 (only when conversions given).

Example

Spend 500, 40,000 impressions, 1,000 clicks, 25 conversions: {"spend":500,"impressions":40000,"clicks":1000,"conversions":25} → {"cpm":12.5,"cpc":0.5,"ctr_percent":2.5,"cpa":20,"conversion_rate_percent":2.5}

Spend 1,200, 250,000 impressions, 3,000 clicks, 60 conversions: {"spend":1200,"impressions":250000,"clicks":3000,"conversions":60} → {"cpm":4.8,"cpc":0.4,"ctr_percent":1.2,"cpa":20,"conversion_rate_percent":2}

GET https://tttkmbb.com/api/v1/calculate/ad-metrics?spend=500&impressions=40000&clicks=1000&conversions=25

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/ad-metrics (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/ad-metrics · Markdown: https://tttkmbb.com/business/ad-metrics.md · JSON definition: https://tttkmbb.com/business/ad-metrics.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="ad-metrics"
OpenAPI operationId: calculate_ad_metrics
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Google Ads Help – Cost-per-thousand impressions (CPM): Definition (reference)
Google Ads Help – Clickthrough rate (CTR): Definition (reference)
Wikipedia – Cost per mille (reference)

FAQ

What does 'mille' in CPM mean?

Latin for thousand: CPM is the cost of 1,000 impressions, so spend / impressions × 1000. A CPM of 12.50 means 1.25 cents per impression.

Is the conversion rate based on clicks or impressions?

On clicks (conversions / clicks), the convention in Google Ads and most ad platforms. Conversions per 1,000 impressions is reported separately.

What if clicks are zero?

CPC and conversion rate are undefined and are omitted; CPM and CTR (0 %) are still returned.

Related calculators

ROAS Calculator — Revenue-based return on the same ad spend.
Conversion Rate Calculator — Conversion rate and required traffic from visitors and conversions.
Ad Revenue Calculator (RPM) — Publisher-side revenue from RPM and page views.