saas-economics-efficiency-metrics skill

Purpose

Determine whether your SaaS business model is fundamentally viable and capital-efficient. Use this to calculate unit economics, assess profitability, manage cash runway, and decide when to scale vs. optimize. Essential for fundraising, board reporting, and making smart investment trade-offs.

This is not a finance reporting tool—it's a framework for PMs to understand whether the business can sustain growth, when to prioritize efficiency over growth, and which investments have positive returns.

Input

Works best with: The question you're answering (can we scale? raise? extend runway?) or the metrics you want evaluated. Also useful: Your numbers — CAC, gross margin, burn, runway, magic number — partial data is workable.

Anything supplied with the invocation itself — text after the skill name, a pasted context dump, or an appended ARGUMENTS: line — counts as answers already given. Use it and skip whatever it covers; don't re-ask.

Arriving empty-handed? That works too. Use it as a reference: read the metric sections relevant to your stage and decision.

Example invocation: Are we efficient enough to scale? CAC $9K, gross margin 72%, burn multiple 2.1, magic number 0.6.

Key Concepts

Unit Economics Family

Metrics that measure profitability at the customer level—the foundation of sustainable SaaS.

Gross Margin — Percentage of revenue remaining after direct costs (COGS).

• Why PMs care: A feature that generates $1M revenue at 80% margin is worth far more than $1M at 30% margin. Margin determines which features to prioritize.
• Formula: (Revenue - COGS) / Revenue × 100
• COGS includes: Hosting, infrastructure, payment processing, customer onboarding costs
• Benchmark: SaaS 70-85% good; <60% concerning

CAC (Customer Acquisition Cost) — Total cost to acquire one customer.

• Why PMs care: Shapes entire go-to-market strategy. Determines which channels are viable and how much you can invest in product-led growth.
• Formula: Total Sales & Marketing Spend / New Customers Acquired
• Benchmark: Varies by model—Enterprise $10K+ ok; SMB <$500 target
• Include: Marketing spend, sales salaries, tools, commissions

LTV (Lifetime Value) — Total revenue expected from one customer over their lifetime.

• Why PMs care: Tells you what you can afford to spend on acquisition. Higher LTV enables premium channels and longer payback periods.
• Formula (simple): ARPU × Average Customer Lifetime (months)
• Formula (better): ARPU × Gross Margin % / Churn Rate
• Formula (advanced): Account for expansion, discount rates, cohort-specific retention
• Benchmark: Must be 3x+ CAC; varies by segment

LTV:CAC Ratio — Efficiency of customer acquisition spending.

• Why PMs care: Is growth sustainable or are you buying revenue at a loss? Determines when to scale vs. optimize.
• Formula: LTV / CAC
• Benchmark: 3:1 healthy; <1:1 unsustainable; >5:1 might be underinvesting
• Note: This ratio alone doesn't tell the full story—also need payback period

Payback Period — Months to recover CAC from customer revenue.

• Why PMs care: Cash efficiency. Faster payback = reinvest sooner. Slow payback can kill growth even with good LTV:CAC.
• Formula: CAC / (Monthly ARPU × Gross Margin %)
• Benchmark: <12 months great; 12-18 ok; >24 months concerning
• Critical: Must have cash to sustain payback period

Contribution Margin — Revenue remaining after ALL variable costs (not just COGS).

• Why PMs care: True unit profitability. Includes support, processing fees, variable OpEx.
• Formula: (Revenue - All Variable Costs) / Revenue × 100
• Variable costs: COGS + support + payment processing + variable customer success
• Benchmark: 60-80% good for SaaS; <40% concerning

Gross Margin Payback — Payback period using actual profit, not revenue.

• Why PMs care: More accurate than simple payback. Shows true cash recovery time.
• Formula: CAC / (Monthly ARPU × Gross Margin %)
• Benchmark: Typically 1.5-2x longer than simple revenue payback

CAC Payback by Channel — Compare payback across acquisition channels.

• Why PMs care: Not all channels are created equal. Optimize channel mix based on payback efficiency.
• Formula: Calculate CAC and payback separately for each channel
• Use: Allocate budget to faster-payback channels when cash-constrained

Capital Efficiency Family

Metrics that measure how efficiently you use cash to grow the business.

Burn Rate — Cash consumed per month.

• Why PMs care: Determines what you can build and when you need funding. High burn requires aggressive revenue growth.
• Formula (Gross Burn): Monthly Cash Spent (all expenses)
• Formula (Net Burn): Monthly Cash Spent - Monthly Revenue
• Benchmark: Net burn <$200K manageable for early stage; >$500K needs clear path to revenue

Runway — Months until cash runs out.

• Why PMs care: Literal survival metric. Dictates timeline for milestones, fundraising, profitability.
• Formula: Cash Balance / Monthly Net Burn
• Benchmark: 12+ months good; 6-12 manageable; <6 months crisis mode
• Rule: Raise when you have 6-9 months runway, not 3 months

OpEx (Operating Expenses) — Costs to run the business (excluding COGS).

• Why PMs care: Your team's salaries live here. Where "efficiency" cuts happen during downturns.
• Categories: Sales & Marketing (S&M), Research & Development (R&D), General & Administrative (G&A)
• Benchmark: Should grow slower than revenue as you scale (operating leverage)

Net Income (Profit Margin) — Actual profit or loss after all expenses.

• Why PMs care: True bottom line. Are you making money? Can you self-fund growth?
• Formula: Revenue - All Expenses (COGS + OpEx)
• Benchmark: Early SaaS often negative (growth mode); mature should be 10-20%+ margin

Working Capital Impact — Cash timing differences between revenue recognition and cash collection.

• Why PMs care: Annual contracts paid upfront boost cash. Monthly billing delays cash. Affects runway calculations.
• Example: $1M annual contract paid upfront = $1M cash now, not $83K/month
• Use: Understand cash vs. revenue timing when planning runway

Efficiency Ratios Family

Composite metrics that measure growth vs. profitability trade-offs.

Rule of 40 — Growth rate + profit margin should exceed 40%.

• Why PMs care: Framework for balancing growth vs. efficiency. Guides when to prioritize profitability over growth.
• Formula: Revenue Growth Rate % + Profit Margin %
• Benchmark: >40 healthy; 25-40 acceptable; <25 concerning
• Example: 60% growth + (-20%) margin = 40 (healthy growth-mode SaaS)
• Example: 20% growth + 25% margin = 45 (healthy mature SaaS)

Magic Number — Sales & marketing efficiency.

• Why PMs care: Is your GTM engine working? Should you scale spend or optimize first?
• Formula: (Current Quarter Revenue - Previous Quarter Revenue) × 4 / Previous Quarter S&M Spend
• Benchmark: >0.75 efficient; 0.5-0.75 ok; <0.5 fix before scaling
• Note: "× 4" annualizes quarterly revenue change

Operating Leverage — How revenue growth compares to cost growth.

• Why PMs care: Are you scaling efficiently? Revenue should grow faster than costs.
• Measure: Revenue growth rate vs. OpEx growth rate over time
• Good: Revenue growth 50%, OpEx growth 30% (positive leverage)
• Bad: Revenue growth 20%, OpEx growth 40% (negative leverage)

Unit Economics — General term for profitability of each "unit" (customer, seat, transaction).

• Why PMs care: Is the business model fundamentally viable at the unit level?
• Calculate: Revenue per unit - Cost per unit
• Requirement: Positive contribution required; aim for >$0 after all variable costs

Anti-Patterns (What This Is NOT)

• Not vanity metrics: High LTV means nothing if payback takes 4 years and customers churn at 3 years.
• Not static benchmarks: "Good" CAC varies wildly by business model (PLG vs. enterprise sales).
• Not isolated numbers: LTV:CAC ratio without payback period can mislead (great ratio, terrible cash efficiency).
• Not just finance's problem: PMs must own unit economics—every feature decision impacts margins and CAC.

When to Use These Metrics

Use these when:

• Evaluating whether to scale acquisition (LTV:CAC, payback, magic number)
• Deciding feature investments (margin impact, contribution to LTV)
• Planning runway and fundraising (burn rate, runway, Rule of 40)
• Comparing customer segments or channels (unit economics by segment)
• Board/investor reporting (Rule of 40, magic number, LTV:CAC)
• Choosing between growth and profitability (Rule of 40 trade-offs)

Don't use these when:

• Making decisions without revenue context (pair with saas-revenue-growth-metrics)
• Comparing across wildly different business models without normalization
• Early product discovery (pre-revenue focus on PMF, not unit economics)
• Short-term tactical decisions (use engagement metrics, not LTV)

Application

Step 1: Calculate Unit Economics

Use the templates in template.md to calculate your unit economics metrics.

Gross Margin