CAC Payback Period Calculator: Measure Marketing Spend Sustainability
Calculate your customer acquisition cost payback period, LTV:CAC ratio, and runway impact to determine if your marketing spend is sustainable for long-term growth. For SaaS companies, target payback periods under 12 months and LTV:CAC ratios above 3:1. Results shown in GBP with USD conversion. Learn more about marketing budget allocation or explore our marketing strategy services to optimize your unit economics.
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Explanation of the formula / methodology
This calculator helps you assess the sustainability of your customer acquisition economics by measuring how quickly you recover the cost of acquiring a customer and whether your lifetime value justifies the acquisition cost.
Payback Period: Calculated as CAC ÷ (Monthly Revenue × Gross Margin %). This shows how many months it takes to recover the cost of acquiring a customer. For SaaS companies, target payback periods under 12 months indicate healthy unit economics.
LTV:CAC Ratio: Calculated as LTV ÷ CAC. This ratio indicates the return on acquisition investment. A ratio above 3:1 is considered healthy for SaaS companies, meaning each customer generates at least 3x their acquisition cost over their lifetime.
Runway Impact: If you provide current runway and monthly burn rate, this shows how much each customer acquisition reduces your runway. This helps assess the sustainability of scaling customer acquisition.
These metrics are benchmarks for SaaS companies. Adjust targets based on your industry, business model, and growth stage. Consider regional differences and funding status when interpreting results.
Tips for using the calculator
Use average CAC and LTV values based on recent customer cohorts (last 3-6 months) for most accurate results.
If payback exceeds 12 months, focus on reducing CAC through channel optimization or increasing pricing/contribution margin.
If LTV:CAC is below 3:1, prioritize improving retention, increasing upsells, or optimizing pricing to improve lifetime value.
Monitor these metrics monthly and track trends over time. Unit economics can degrade as you scale if not actively managed.
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