Substack Free-to-Paid Subscriber Conversion Tracker

Project your Substack growth, paid conversions, monthly churn, and net publisher earnings over time with this interactive simulator.

Mathematical Audit

Subscriber Growth & Conversion Formulas

Model free subscriber growth and forecast monthly paid conversions and churn rates over a custom projection period.

Free Subscribers (t) = Free Subscribers (t-1) × (1 + Growth Rate ÷ 100)
Target Paid Subscribers (t) = Free Subscribers (t) × (Conversion Rate ÷ 100)
New Paid Subscribers (t) = Target Paid Subscribers (t) - Active Paid (t-1) (with minimum 0)
Churned Paid (t) = Active Paid (t-1) × (Monthly Churn Rate ÷ 100)
Active Paid (t) = Active Paid (t-1) + New Paid (t) - Churned Paid (t)
Substack Fee = Gross Subscription Revenue × 10%
Stripe Fee = (Revenue × 2.9%) + (Transactions × $0.30)

Subscription revenue balances monthly and annual paying members based on your annual subscription split ratio.

Operational Guide

How to Project Newsletter Conversions

1

Input current free list size

Enter the number of active free subscribers currently on your Substack newsletter.

2

Set monthly free list growth rate

Input the estimated percentage monthly growth you expect for your free list (e.g. 5%).

3

Select your free-to-paid conversion rate

Enter the percentage of your list that is paying for subscriptions (industry standards range from 1.5% to 3.0%).

4

Input subscription prices and splits

Set your monthly and annual price tiers, alongside the percentage of paid subscribers choosing annual billing.

5

Define monthly churn rate and projection period

Enter your subscriber churn rate and the number of months to model (up to 24 months).

Real-World Scenario Example

"A writer has 5,000 free subscribers, grows their list at 5% monthly, converts at 2.0% to paid, charging $5/mo and $50/yr (with a 20% annual split), experiencing 5% monthly churn."

Inputs

currentFreeSubs:5000
monthlyFreeGrowthRate:5
freeToPaidConversionRate:2
avgMonthlySubPrice:5
avgAnnualSubPrice:50
annualSubSplit:20
monthlyChurnRate:5
projectionMonths:12

Result

Month 12 free list: 8,552. Month 12 active paid: 153. Year-end gross monthly revenue: $711.23. Annualized net profit: $5,946.22.

Important Disclaimer

Forecast projections are estimations. Actual growth rates, paid conversions, and churn rates fluctuate based on content consistency, niche value, and subscriber payment failures.

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