Ad Metrics Calculator
Calculate ROAS, ACOS, TACOS, CTR, CPC, CPM, conversion rate, impression share, frequency, LTV:CAC ratio, and blended CAC for Google Ads or Meta Ads — with the exact formula behind every number.
How each metric is calculated
ROAS (Return on Ad Spend) = Revenue ÷ Ad Spend, shown as a multiple (e.g. 4.0x means every $1 spent returned $4 in revenue). It's the headline profitability metric on both Google Ads and Meta Ads Manager.
ACOS (Advertising Cost of Sale) = Ad Spend ÷ Revenue × 100, shown as a percentage. It's mathematically the inverse of ROAS (ACOS = 100 ÷ ROAS) — Amazon Ads popularized this term, though the same ratio is sometimes called "Cost Per Acquisition of Sale" elsewhere.
TACOS (Total Advertising Cost of Sale) = Ad Spend ÷ Total Business Revenue × 100. Unlike ACOS, the denominator is your entire revenue — ads-attributed and organic — so TACOS captures how much ads are costing you relative to your whole business, including any halo effect on unpaid sales.
CTR (Click-Through Rate) = Clicks ÷ Impressions × 100. Both Google Ads and Meta report this identically.
CPC (Cost Per Click) = Ad Spend ÷ Clicks. CPM (Cost Per Mille) = Ad Spend ÷ Impressions × 1,000, the cost to reach 1,000 impressions.
Conversion Rate = Conversions ÷ Clicks × 100. CPA (Cost Per Acquisition) = Ad Spend ÷ Conversions.
Impression Share = Impressions Received ÷ Total Eligible Impressions × 100. This is the one metric on this page you can't fully derive yourself — the eligible-impressions denominator is estimated by Google/Meta's auction system using data (competitor bids, inventory, targeting overlap) that isn't visible to advertisers, so treat this field as an estimate or the platform-reported figure if you have it.
Frequency = Impressions ÷ Reach, the average number of times a unique person saw your ad. Meta surfaces this directly; Google Ads calls the same ratio "Impr./Reach" in some reports.
LTV:CAC Ratio = Customer Lifetime Value ÷ Cost Per Acquisition. A commonly cited healthy benchmark is 3:1 or higher — below that, you're likely spending too much to acquire customers relative to what they're worth over time; well above 5:1 can also signal you're under-investing in growth.
Blended CAC = Combined Spend Across Channels ÷ Combined Conversions Across Channels. This differs from a single channel's CPA because it captures cross-channel assist effects (a customer who saw a Meta ad but converted via Google Search, for example) that per-channel attribution can double-count or miss entirely.
Metric breakdown
Run the calculator above to see all metrics compared on one chart.
Common mistakes
- Confusing ROAS and ACOS direction. Higher ROAS is better (more revenue per dollar spent); higher ACOS is worse (more spend per dollar of revenue) — they move in opposite directions even though they measure the same underlying ratio.
- Judging campaigns on ACOS alone, ignoring TACOS. A campaign can hit a great ACOS while cannibalizing organic sales you'd have gotten anyway — TACOS trending flat or down over time is the real signal that ads are driving incremental growth.
- Treating Impression Share as something you can compute exactly from your own data. Unlike CTR or CPC, the eligible-impressions denominator is a platform estimate you don't fully observe, so small swings in reported Impression Share aren't necessarily changes in your account.
- Optimizing one channel's CPA while ignoring Blended CAC. A channel can show a great standalone CPA while total acquisition cost across all channels quietly rises — Blended CAC is the number that reflects true overall efficiency.
- Ignoring frequency until ad fatigue already hurt performance. Frequency climbing much above 3-4x within a short window on the same audience is a common early signal of rising ad fatigue and falling CTR, before it shows up clearly in ROAS.
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Frequently Asked Questions
What is the difference between ROAS and ACOS?
They're inverses describing the same relationship. ROAS = Revenue ÷ Ad Spend, expressed as a multiple (e.g. 4x). ACOS = Ad Spend ÷ Revenue, expressed as a percentage (e.g. 25%). A 4x ROAS is exactly the same performance as a 25% ACOS.
What is the difference between ACOS and TACOS?
ACOS only looks at revenue the ad platform directly attributes to ads. TACOS (Total Advertising Cost of Sale) divides ad spend by your total business revenue, including organic and non-ad sales, so it captures the halo effect ads have on unpaid sales that ACOS misses.
How is impression share calculated?
Impression Share = Impressions you actually received ÷ Total impressions you were eligible to receive, shown as a percentage. Google Ads and Meta both estimate the eligible-impressions denominator using auction and inventory data you don't fully see, so it's a platform-reported metric rather than one you can derive purely from your own numbers.
What's a good LTV:CAC ratio?
3:1 or higher is a commonly cited healthy benchmark — it means a customer is worth at least 3x what it costs to acquire them. Below 1:1 means you're losing money on acquisition before accounting for margin; well above 5:1 can suggest you could be investing more aggressively in growth.
Why does Blended CAC differ from a single channel's CPA?
Blended CAC divides total spend across all channels by total conversions across all channels, capturing cross-channel assist effects that per-channel attribution can miss or double-count — it's the more reliable number for judging overall acquisition efficiency.