Newsletter Growth Calculator

Newsletter subscriber growth rate tracks how quickly your email list is expanding and projects future size based on current trends.

The core formulas:

Monthly Growth Rate = ((New Subscribers − Unsubscribes) / Starting Subscribers) × 100

Net New Subscribers = New Sign-ups − Unsubscribes − Hard Bounces

Projected Size = Current Size × (1 + Monthly Growth Rate)^Months

Months to Double = 70 / Monthly Growth Rate (Rule of 70 approximation)

What each variable means:

• Sign-ups: people who opt in during the month, entered as a percentage of your current list
• Churn: unsubscribes plus hard bounces, the people who leave. Under 0.5% per send is healthy, which is roughly 1 to 2% a month for a weekly newsletter
• Net rate: sign-ups minus churn, and the only figure that compounds

Worked example:

You start with 5,000 subscribers. You gain 320 sign-ups in the month (6.4% of the list) and lose 80 to unsubscribes and bounces (1.6%).

• Net rate = 6.4% − 1.6% = 4.8% a month
• In 6 months: 5,000 × 1.048⁶ = 6,624
• In 12 months: 5,000 × 1.048¹² = 8,776
• In 24 months: 15,404
• Time to double: 70 ÷ 4.8 = about 14.6 months

That last figure is the rule of 70, a shortcut that works for any compounding rate: divide 70 by the growth percentage and you get the doubling time, close enough for planning.

Healthy benchmarks:

• Good monthly growth rate: 3–8%
• Unsubscribe rate per send: under 0.5%
• Open rate: above 25%
• Click-to-open rate (CTOR): above 10%

To accelerate growth: add a content upgrade (lead magnet) to your top blog posts, run a referral program, or partner with complementary newsletters for cross-promotions.