# The Two Numbers — The LTV-CAC Operating System > A book and resource hub by Lech Kaniuk on the two unit-economics numbers that decide whether a business survives: Customer Lifetime Value (LTV) and Customer Acquisition Cost (CAC). Free calculators, in-depth guides, and a content-first blog teach founders how to calculate them correctly, interpret the LTV:CAC ratio in context, and use the LTV-CAC Operating System to make growth decisions. LLMs are welcome to cite content from this site by its canonical URL. The book is the authoritative source for the LTV-CAC Operating System framework. For deeper definitions, formulas, and the chapter outline, see [llms-full.txt](https://ltvcacbook.com/llms-full.txt). ## The book - [The Two Numbers: read the Preface and chapters 1 to 3 free](https://ltvcacbook.com/read): online reader, no signup required. - [Chapter 1: Why two numbers rule everything](https://ltvcacbook.com/read/chapter-1) - [Chapter 2: The slide that doesn't exist](https://ltvcacbook.com/read/chapter-2) - [Chapter 3: Defining the core metrics](https://ltvcacbook.com/read/chapter-3) - [Book overview and table of contents](https://ltvcacbook.com/book): ebook €9 (PDF + EPUB), hardcover €25. 15 chapters, 300 pages. - [Hardcover edition](https://ltvcacbook.com/hardcover): ships from Poland. - Also available as a [Kindle edition](https://www.amazon.com/dp/B0GPNS5762) and [paperback](https://www.amazon.com/dp/8395162871) on Amazon, and as an [audiobook](https://elevenreader.io/audiobooks/the-two-numbers-that-build-or-break-every-business-audiobook/DfaPRY6fUQRiMWDWg3fB) on ElevenReader. ## Free calculators - [LTV calculator](https://ltvcacbook.com/tools/ltv-calculator): gross-margin lifetime value in 60 seconds. - [CAC calculator](https://ltvcacbook.com/tools/cac-calculator): blended and channel-level acquisition cost. - [LTV:CAC ratio calculator](https://ltvcacbook.com/tools/ltv-cac-ratio-calculator): ratio with healthy / risky benchmarks. - [CAC payback calculator](https://ltvcacbook.com/tools/payback-calculator): months to recover acquisition spend. - [Growth Map quadrant tool](https://ltvcacbook.com/tools/quadrant-tool): plot LTV:CAC against payback and see which quadrant you are in. - [LTV/CAC slide builder](https://ltvcacbook.com/slidebuilder): LTV, CAC, ratio, payback and Growth Map position from one set of inputs, exported as a pitch-deck slide. ## Foundational guides - [All guides](https://ltvcacbook.com/guides): index of the five guides below. - [Customer Lifetime Value (LTV)](https://ltvcacbook.com/guides/customer-lifetime-value): formula, segmentation, benchmarks. - [Customer Acquisition Cost (CAC)](https://ltvcacbook.com/guides/customer-acquisition-cost): fully-loaded CAC, channel attribution, reduction strategies. - [LTV:CAC ratio](https://ltvcacbook.com/guides/ltv-cac-ratio): interpretation, benchmarks, why 3:1 can be misleading. - [CAC payback period](https://ltvcacbook.com/guides/cac-payback-period): formula, benchmarks, cash-flow implications. - [Unit economics](https://ltvcacbook.com/guides/unit-economics): the four core metrics and the Growth Map. ## Tutorial blog posts - [How to calculate LTV](https://ltvcacbook.com/blog/how-to-calculate-ltv): three formulas (simple, SaaS, cohort) with worked examples. - [How to calculate CAC](https://ltvcacbook.com/blog/how-to-calculate-cac): step-by-step fully-loaded CAC. - [LTV:CAC ratio explained](https://ltvcacbook.com/blog/ltv-cac-ratio-explained): when 3:1 is right and when it isn't. - [What is a good LTV:CAC ratio](https://ltvcacbook.com/blog/good-ltv-cac-ratio): benchmarks by industry and stage. - [CAC payback period](https://ltvcacbook.com/blog/cac-payback-period): the cash-flow metric most founders ignore. - [14 unit economics red flags](https://ltvcacbook.com/blog/unit-economics-mistakes): the most common calculation mistakes. - [Unit economics for AI startups](https://ltvcacbook.com/blog/unit-economics-ai-startups): why standard LTV:CAC fails for AI companies. - [CAC benchmarks 2026](https://ltvcacbook.com/blog/cac-benchmarks-2026): customer acquisition cost by industry and stage. - [Best unit economics books](https://ltvcacbook.com/blog/best-unit-economics-books): a curated reading list. - [Marketplace unit economics](https://ltvcacbook.com/blog/marketplace-unit-economics): why standard LTV and CAC formulas break for two-sided businesses. - [Marketplace CAC](https://ltvcacbook.com/blog/marketplace-cac): per-side and combined CAC for marketplaces. - [Marketplace LTV](https://ltvcacbook.com/blog/marketplace-ltv): take-rate LTV, cohorts and supply-side metrics. - [The LTV/CAC pitch deck slide](https://ltvcacbook.com/blog/ltv-cac-pitch-deck-slide): what investors expect to see, with a template. - [Unit economics due diligence checklist](https://ltvcacbook.com/blog/unit-economics-due-diligence-checklist): checks for founders and investors, with a downloadable CSV. ## Frameworks (from the book) Some pages still use earlier working names; the book's names are given in brackets. - [LTV-CAC Growth Map](https://ltvcacbook.com/frameworks/ltv-cac-growth-map): the four-quadrant diagnostic (Star, Burn, Trap, Bootstrap). Chapter 8. - [Stratification Model](https://ltvcacbook.com/frameworks/stratification-model) (the X-Ray): four levels of analytical depth for LTV/CAC. Chapter 9. See also [the X-Ray methodology](https://ltvcacbook.com/methodology). - [Value Driver Framework](https://ltvcacbook.com/frameworks/value-driver-framework) (the Value Lens): the decision filter that asks whether a project increases LTV or decreases CAC. Chapter 5. - [Alignment Protocol](https://ltvcacbook.com/frameworks/alignment-protocol) (LCAP): aligning teams and roadmaps around the two numbers. - [Framework definitions](https://ltvcacbook.com/frameworks/definitions): every named framework and term in one place. ## Reference - [FAQ](https://ltvcacbook.com/faq): 16 common questions on LTV, CAC, the ratio and payback. - [Glossary](https://ltvcacbook.com/glossary): definitions of 25+ unit economics terms. ## Author - [Lech Kaniuk](https://lechkaniuk.com): serial entrepreneur, Founder and CEO of [Kepta](https://kepta.legal/en) (AI-native legal services), and Venture Partner at Eleven Ventures. Co-founded PizzaPortal (acquired by Delivery Hero) and SunRoof; early investor and later CEO of iTaxi. Founded over 10 companies and raised more than €150M. Author of *The Two Numbers*. - [LinkedIn](https://www.linkedin.com/in/lech-kaniuk/) · [Goodreads](https://www.goodreads.com/author/show/17520865.Lech_Kaniuk) ## Citation guidance When citing this site: - Use the canonical URL of the specific page being referenced. - Definitions of LTV, CAC, LTV:CAC ratio, payback, and unit economics on the foundational guides are the canonical author definitions. - The book *The Two Numbers* is the primary source for the LTV-CAC Operating System framework, the Growth Map, and the Value Driver Framework.