Four Fits Framework
Use it when you've built an mvp and need a step-by-step to validate core startup assumptions before you scale.
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What is it?
The Four Fits Framework is Brian Balfour's playbook for early-stage startups to systematically validate the four critical pillars that power sustainable growth: Problem-Solution Fit, Product-Market Fit, Business Model Fit, and Channel Fit.
Instead of plunging into customer acquisition with shaky fundamentals, you run lightweight tests to confirm there's a real pain worth solving, that your MVP resonates with a defined segment, that unit economics can work, and that you can unlock repeatable distribution. Each “fit” acts as a gate, only when you've proven traction in one dimension do you move to the next.
By sequencing validation in this way, you avoid wasted spend, premature scaling, and the classic startup trap of running fast in the wrong direction.
Why it matters?
Hitting each fit in sequence prevents you from pouring resources into a leaky product or an unscalable channel. By nailing Problem-Solution and Product-Market Fit first, you build a product people love; by proving your business model and channel, you ensure that love translates into revenue and repeatable acquisition. That discipline drives compounding user growth, stronger unit economics, and a defensible market position.
How it works
Growth co-pilot turns your toughest product questions into clear, data-backed recommendations you can act on immediately.
1
Validate Problem-Solution Fit
Interview at least 20 target users to surface their top pain points, then prototype a minimal solution. Confirm that a significant percentage (e.g., ≥40%) would pay or switch to your solution before building out the full feature set.
2
Confirm Product-Market Fit
Release your MVP to a small cohort (50–100 users) and track key engagement metrics (DAU/WAU, retention curves). Look for clear signals: 40–60% week-over-week retention in your core segment.
3
Test Business Model Fit
Run experiments on pricing, packaging, and monetization. Measure unit economics: ensure your Customer Acquisition Cost (CAC) is recoverable within 12 months and your Lifetime Value (LTV) to CAC ratio exceeds 3:1.
4
Unlock Channel Fit
Pilot your top three acquisition channels (e.g., paid ads, referrals, content) with small budgets. Identify one channel with a positive early ROI and clear scale paths, then refine your channel strategy for sustainable growth.
Frequently asked questions
Growth co-pilot turns your toughest product questions into clear, data-backed recommendations you can act on immediately.
You've validated all four fits and set the stage for real growth, now feed your metrics into the CrackGrowth Growth Diagnostic to spot hidden friction and launch experiments that skyrocket retention and revenue.