# Finances > Use this skill when the user needs to build a financial model, calculate unit economics, understand MRR/ARR/churn, or figure out their quit number. Covers SaaS metrics, CAC/LTV, burn rate, cash flow modeling, and making unit economics legible for non-finance founders. - Skill: `whawkinsiv/finances` (Agent Skill) - Install (CLI): `npx skillmds add whawkinsiv/finances` - Raw SKILL.md: https://api.skillmd.com/api/skills/whawkinsiv/finances/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: whawkinsiv (https://skillmd.com/u/whawkinsiv) - Updated: 2026-09-09 - Page: https://skillmd.com/skills/whawkinsiv/finances --- # SaaS Financial Modeling & Metrics A SaaS business is a math machine. If you don't know your numbers, you're guessing. This skill makes unit economics legible — MRR, CAC, LTV, churn, burn rate — clear enough to make decisions, rigorous enough to be trusted. ## Core Principles - A SaaS business is a math machine. If you don't know your numbers, you're guessing. - Unit economics tell the truth about your business long before your bank account does. - The only financial model that matters for a solo founder is one that fits on a single spreadsheet and gets updated monthly. - Revenue is vanity. Margin is sanity. Cash flow is reality. - Every metric should answer a specific question: "Should I spend more here?" or "Is this working?" ## The Quit Number Before building anything, calculate what it takes to replace your income: ``` Monthly personal burn (after taxes): Rent/mortgage: $______ Insurance: $______ Food/living: $______ Debt payments: $______ Everything else: $______ Safety buffer (20%): $______ = Monthly nut: $______ Required MRR to quit: Monthly nut ÷ 0.70 = $______ (0.70 accounts for taxes, SaaS costs, and variance) At your target price point ($X/mo): Required MRR ÷ Price = customers needed Timeline: Customers needed ÷ realistic monthly growth rate = months to quit ``` **Reality check**: If you need 500+ customers at $29/mo to quit, that's an 18-36 month journey. Plan accordingly. ## Personal Constraint Budget ``` Runway calculation: Current savings available for this venture: $______ Monthly burn while building (no revenue): $______ Savings ÷ Monthly burn = months of runway: ______ Hard deadline: Date you MUST have revenue or go back to employment. Startup costs (one-time): Domain + hosting (year 1): $100-500 LLC formation: $50-500 Tools (analytics, email): $0-200/mo Paid acquisition test: $500-1,000 Legal (if needed): $500-2,000 = Total launch cost: $______ Monthly operating costs (once live): Hosting/infra: $______ SaaS tools: $______ Email service: $______ Payment fees: $______ = Monthly opex: $______ ``` ## Core SaaS Metrics ### The Metrics That Matter (and only these) **Monthly Recurring Revenue (MRR)** ``` MRR = Sum of all active monthly subscription amounts MRR breakdown: New MRR: Revenue from new customers this month Expansion MRR: Revenue from upgrades/seat additions Contraction MRR: Revenue lost from downgrades Churned MRR: Revenue lost from cancellations Net New MRR: New + Expansion - Contraction - Churned ``` **Annual Recurring Revenue (ARR)** ``` ARR = MRR × 12 (Only use this once MRR is relatively stable. Don't annualize your first month.) ``` **Customer Acquisition Cost (CAC)** ``` CAC = Total acquisition spend ÷ New customers acquired (in same period) Include: Ad spend, outreach tools, content costs, your time (value it at $0 for solo founder or at your opportunity cost — be consistent). By channel: SEO CAC: Content costs ÷ SEO-attributed signups Paid CAC: Ad spend ÷ Paid-attributed signups Outreach CAC: Tool costs ÷ Outreach-attributed signups ``` **Lifetime Value (LTV)** ``` Simple LTV: LTV = ARPU ÷ Monthly churn rate Example: ARPU = $49/mo, Monthly churn = 5% LTV = $49 ÷ 0.05 = $980 With gross margin: LTV = (ARPU × Gross margin %) ÷ Monthly churn rate ``` **LTV:CAC Ratio** ``` LTV:CAC = LTV ÷ CAC Benchmarks: < 1:1 You lose money on every customer. Stop spending. 1-3:1 Unsustainable. Improve retention or reduce CAC. 3:1 Healthy target for most SaaS. > 5:1 You're probably underinvesting in growth. ``` **CAC Payback Period** ``` Payback = CAC ÷ (ARPU × Gross margin %) Example: CAC = $150, ARPU = $49/mo, Gross margin = 85% Payback = $150 ÷ ($49 × 0.85) = 3.6 months Benchmarks: < 6 months: Excellent for solo founder 6-12 months: Acceptable > 12 months: Dangerous without funding ``` **Churn Rate** ``` Logo churn (customer count): Customers lost this month ÷ Customers at start of month Revenue churn (MRR): MRR lost this month ÷ MRR at start of month Net revenue retention (NRR): (MRR at start + Expansion - Contraction - Churn) ÷ MRR at start NRR > 100% means existing customers grow faster than they churn. Benchmarks: Logo churn < 5%/mo: Acceptable early stage Logo churn < 3%/mo: Good Revenue churn < 2%/mo: Target NRR > 100%: Excellent (expansion revenue working) ``` ## Unit Economics Calculation Build this table monthly: ``` | Metric | Month 1 | Month 2 | Month 3 | ... | |---------------------------|---------|---------|---------|-----| | New customers | | | | | | Churned customers | | | | | | Total customers (end) | | | | | | MRR | | | | | | Net new MRR | | | | | | Revenue (collected) | | | | | | COGS (hosting, APIs, etc) | | | | | | Gross profit | | | | | | Gross margin % | | | | | | Total acquisition spend | | | | | | CAC | | | | | | LTV | | | | | | LTV:CAC | | | | | | Payback (months) | | | | | | Operating expenses | | | | | | Net profit/loss | | | | | | Cash balance | | | | | | Runway (months) | | | | | ``` ## Revenue Mix Model Map your revenue sources: ``` Primary revenue: Monthly subscriptions: $X/mo × estimated customers = $______ Annual subscriptions: $Y/yr × estimated customers = $______ Secondary revenue (if applicable): Usage-based overage: Estimated average overage/customer = $______ One-time setup fees: $Z × new customers/month = $______ Consulting/services: Hours/month × rate = $______ Revenue mix target: Recurring %: ____% (target >80%) One-time %: ____% (keep <20%) Services %: ____% (keep <10% — doesn't scale) ``` ## Essential Metrics Dashboard Track weekly, review monthly: **Growth metrics:** - MRR (absolute and growth rate) - New signups this week - Activation rate (signups → activated) - Conversion rate (activated → paying) **Retention metrics:** - Monthly logo churn rate - Monthly revenue churn rate - Net revenue retention **Economics metrics:** - CAC by channel - LTV:CAC ratio - Gross margin % - Cash runway (months) **Leading indicators (predict future revenue):** - Traffic to marketing site - Trial starts - Feature adoption rates - Support ticket volume (rising = problems ahead) ## Financial Forecasting (Simple) Don't build a complex model. Use this: ``` Conservative monthly growth rates by stage: Pre-revenue to $1K MRR: add 5-15 customers/month $1K-$5K MRR: 10-20% MRR growth/month $5K-$20K MRR: 5-15% MRR growth/month $20K+ MRR: 3-8% MRR growth/month 3-month forecast: Current MRR × (1 + monthly growth rate)^3 = projected MRR Break-even forecast: Monthly opex ÷ ARPU = customers needed to break even Customers needed ÷ monthly new customers = months to break even ``` ## When the Numbers Say Stop Red flags that mean pivot or stop: - LTV:CAC < 1 after 3+ months of trying to improve it - Monthly churn > 10% with no clear fix - CAC increasing month over month despite optimizations - Activation rate < 20% (product-market fit problem) - Revenue plateaus for 3+ months despite active effort - Cash runway < 3 months with no path to profitability ## Related Skills - **accounting** — Bookkeeping, tax prep, and financial operations - **pricing** — Set prices that support healthy unit economics - **analytics** — Track the product metrics that feed financial models - **ads** — CAC tracking and paid acquisition budgeting