Key metrics for consumer startups: growth, retention, and NPS

Executive overview

Consumer startups face different measurement challenges than B2B: monetisation comes later, users don't have contracts, and churn is harder to define. The metrics that matter most are organic growth rate, unit economics per customer, retention (or a proxy for it), and net promoter score.

Viral loops and network effects are the only sustainable growth engine — paid acquisition returns to zero the moment you stop spending.

Growth rate targets

• 15% month-over-month is good — 5x user base per year
• 10% monthly is acceptable — approximately 3x per year
• Below 5% monthly is unlikely to reach breakout success

Organic vs paid growth

• Organic growth = anything you don't pay for: virality and network effect
• Virality: one user's activity directly introduces others (e.g. Wordle score-sharing, Facebook photo tagging)
• Network effect: product becomes more valuable as more people join (e.g. WhatsApp)
• Best consumer companies run 80–100% organic; 50% organic is acceptable; below 50% is a long-term problem
• Paid referral schemes ("member get member") should be treated as paid acquisition — cannibalization and fraud are real risks
• Ad platforms (Google, Meta) are optimised to extract your margin; heavy reliance on them compresses profit to zero

Building viral loops and network effects

• Identify shareable moments: achievements, milestones, completions users want to broadcast
• Use native iOS/Android sharing prompts to reduce friction
• Shift product thinking from single-player to multiplayer — how does the product improve with more users?
• Viral loop and network effect optimisation compounds forever; ad spend disappears the day you stop

Paid growth tracking

• Use UTM referrers or ask users at sign-up where they heard about you
• Record acquisition channel per user in the database permanently — cohort performance by channel reveals true lifetime value
• Measure customer acquisition cost (CAC) to an active, retained user — not a raw sign-up
• 80–90% early drop-off is common; a sign-up is not a good user

Unit economics

• Unit economics = revenue per customer minus variable costs per customer
• Variable costs include: card issuance, customer service contacts, fraud, wire fees — anything that scales with customer count
• Fixed costs (engineering salaries, office rent) are excluded from unit economics
• Granular tracking by cohort and acquisition channel reveals which customers are profitable
• Scaling negative unit economics destroys capital fast — fix them before scaling (Monzo hit -£30–40/customer/year at 500k users)

Retention and the magic moment

• Define an active user relative to natural usage frequency: daily for Facebook, weekly for Monzo (one transaction), potentially annual for Airbnb
• When the retention period is long, identify a magic moment: an early behaviour that predicts long-term retention
• Find it by comparing behaviour of best users vs. those who churned
• Facebook: adding 7 friends in the first 10 days predicted retention
• Monzo: adding 3 contacts for peer-to-peer payments improved retention by ~20 percentage points
• Re-engineer onboarding to push as many users as possible to hit the magic moment early
• Don't over-optimise the exact threshold — the tipping point matters more than the precise number

Net promoter score

• NPS = % promoters (score 9–10) minus % detractors (score 0–6); passives (7–8) are ignored
• Range: -100 to +100
• Minimum baseline for a new consumer startup: +50
• Strong consumer companies typically score +75 to +96; legacy incumbents often score zero or negative
• High NPS correlates directly with word-of-mouth referral
• Consistency matters: always ask the same question at the same point in the user journey — changing collection method can shift NPS by 20 points overnight
• After the score question, ask an open qualitative "why?" — use detractor feedback to drive targeted fixes