CAC Payback Period Calculator Spreadsheet

You can have profitable unit economics on paper and still run out of cash. The culprit? CAC payback period—the time between spending to acquire a customer and when they repay that cost.

If payback takes 12 months and you're growing 50% year-over-year, you're constantly funding a larger acquisition deficit. Cash goes out today. Cash comes back next year. Many "profitable" ecommerce businesses fail because they run out of runway before payback completes.

This spreadsheet calculates the number that determines how fast you can grow.

🎯 What You'll Get:

A comprehensive CAC payback calculator designed for Australian ecommerce operators. Calculate payback period by channel, understand cash flow implications, and optimize the four levers that accelerate recovery.

✓ Calculate CAC payback period by acquisition channel

✓ Understand cash flow requirements for growth

✓ Compare payback across customer segments

✓ Identify channels with fastest cash recovery

✓ Model working capital needs at different growth rates

✓ Track path to first-order profitability

✓ Measure Payback Velocity Index (PVI)

📊 What's Inside:

• CAC Payback Formula Calculator – Months until customer repays acquisition cost

• Channel Payback Analysis – Compare recovery time across paid channels

• Segment Payback Matrix – High-intent vs. discovery vs. referral customers

• Cash Flow Impact Model – Calculate working capital tied up in acquisition

• First-Order Payback Calculator – Path to immediate profitability

• Four Lever Optimization Framework – Reduce CAC, increase margin, accelerate velocity, front-load revenue

• 60-Day Payback Sprint – Systematic optimization protocol

• Payback Velocity Index (PVI) – New north star metric combining speed and return

• Growth Capacity Calculator – Maximum acquisition rate given cash constraints

🔴 Why Payback Matters More Than LTV:CAC:

Most operators obsess over LTV:CAC ratio. But a 3:1 ratio with 6-month payback is fundamentally different from 3:1 with 24-month payback.

Same ratio. Radically different cash flow.

Scenario A (4-month payback): Reinvest acquisition dollars 3x per year

Scenario B (16-month payback): Reinvest once per year

Over 3 years, Scenario A compounds acquisition efficiency dramatically.

Payback period determines growth capacity. LTV:CAC determines whether growth is profitable.

🔧 Payback Benchmarks by Business Model:

• Subscription (consumables): 3-6 months target, 6-9 acceptable

• Repeat purchase (fashion/beauty): 6-9 months target, 9-12 acceptable

• Occasional purchase (home/gifts): 9-12 months target, 12-18 acceptable

• One-time purchase: First order must be profitable

🇦🇺 Australian Ecommerce Context:

• AUD currency formatting

• Local shipping cost structures

• Realistic contribution margins by category

• Australian payment processing rates

💡 The Cash Flow Reality:

A business acquiring 500 customers/month at $80 CAC with 10-month payback needs $400,000 permanently tied up in customer acquisition.

To grow 50% to 750 customers/month requires an additional $200,000.

This is why fast-growing ecommerce needs capital—not because they're unprofitable, but because payback creates structural working capital requirements.

⚡️ The Four Optimization Levers:

1. Reduce CAC (20% reduction = 20% payback improvement)

2. Increase contribution margin (5pp increase = meaningful acceleration)

3. Increase purchase velocity (2.4 to 3.0 orders/year = 25% improvement)

4. Front-load revenue (higher first-order AOV accelerates recovery)

🎯 First-Order Payback: The Holy Grail

When first-order contribution margin exceeds CAC, you achieve first-order payback—every new customer funds their own acquisition immediately. This enables self-funded growth without external capital.

The calculator shows exactly what AOV, margin, or CAC you need to reach this milestone.

⚡️ Includes:

• Complete payback formulas and benchmarks

• Channel-by-channel comparison templates

• Working capital requirement models

• 60-day optimization sprint roadmap

• Payback Velocity Index calculator

• Self-funding growth threshold analysis

⚡️ Free Download – No email required.

From the team at Uncommon Insights, helping Australian ecommerce operators understand the cash flow mechanics that enable or constrain sustainable growth.