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Inboxwise Tools

Email List Growth Calculator

See where your list could be in a few months — and how much unsubscribes hold it back.

This is a simulation, not a prediction. It assumes your signups and unsubscribe rate stay the same every month. Real lists move with seasons, promotions and list cleaning.

Active subscribers today.

Average monthly signups.

Unsubscribes + bounces + complaints ÷ list size, per month.

1 to 60 months.

Results

Subscribers at the end

—

Total growth

—

vs. today

Long-run ceiling

—

Where the list levels off if nothing changes

Three scenarios

Conservative: 25% fewer signups and 50% higher unsubscribe rate. Optimistic: 25% more signups and 25% lower unsubscribe rate.

    Month by month (your inputs)

    MonthStart+ New− LostEnd

    How the simulation works

    End of month = Start + New subscribers − (Start × Unsubscribe rate)

    Unsubscribes are applied to the list size at the start of each month. Results are rounded for display only.

    The ceiling: why lists stop growing

    If you add the same number of people every month and lose the same percentage every month, your list eventually levels off. That ceiling is simply:

    Ceiling = New subscribers per month ÷ Monthly unsubscribe rate

    With 200 signups a month and a 2% monthly unsubscribe rate, the list tops out around 10,000. Cutting unsubscribes to 1% doubles the ceiling to 20,000 — the same effect as doubling your signups. That's why list hygiene and relevant content matter as much as new opt-in forms.

    How to estimate your unsubscribe rate

    Add up everyone who left your list last month — unsubscribes, hard bounces and spam complaints — and divide by your list size at the start of the month. Average a few months for a steadier number.

    Next: see what that list is worth with the ROI Calculator, or measure engagement with the Open Rate Calculator.

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