Newsletter growth calculator
The panel takes today’s net rate and compounds it, so its curve rises for ever. Real lists do not, because churn is a percentage of a growing list while signups are usually a flat number driven by traffic. Divide your signups by your churn rate for the ceiling that follows: 350 ÷ 2% is 17,500, the size at which departures equal arrivals. Halving churn doubles that ceiling; doubling signups only doubles it too, and costs far more. The projection above is a reasonable guide for a year and increasingly generous after that.
The projection takes your current net growth rate and compounds it. On the figures above, 350 in and 100 out of a 5,000 list is 5% a month, so twelve months of compounding gives 8,979. That assumes signups keep pace with the list as it grows, which is the assumption to check before trusting the number.
How to project list growth
Read the two rate rows first, because everything else follows from them. Monthly growth here is net: signups minus losses, over the starting list, which on these figures is 250 ÷ 5,000, or 5%. Monthly churn is losses over the starting list, 100 ÷ 5,000, or 2%. The projection then applies that 5% again and again.
Compounding a net rate assumes signups grow with the list, and for most newsletters they do not. Signups come from traffic, from a form, from a launch; they are a roughly flat number per month that has no idea how many subscribers you already have. Losses are the opposite: unsubscribes and dead addresses scale almost exactly with how many people you are sending to. Feed a flat 350 in against 2% out and the list converges on 350 ÷ 0.02, which is 17,500, the size at which departures cancel arrivals. Above it the list shrinks; below it, it climbs toward it and slows down as it goes.
The gap between the two models is small at first and then enormous. Over twelve months the panel projects 8,979 while the flat-signup model gives about 7,692, a difference you might live with. Over sixty months the panel projects roughly 93,000 and the flat-signup model tops out near 13,800. Use this projection for a year, treat it as optimistic beyond that, and do the ceiling division by hand whenever the horizon is long.
Three rows on this panel describe three different growth stories, on purpose. Net gain per month is the linear view: 250 a month, so 3,000 over the year and a list of 8,000. Gross signups over the period multiplies your flat monthly signups by the months, giving 4,200, and it deliberately does not compound. The headline projection compounds and gives 8,979. None of them is wrong; they answer different questions, and quoting the largest of the three in a board deck is the mistake to avoid.
Two things about the churn number itself. Unsubscribes happen per send, not per month, so a weekly sender at 0.3% a send loses roughly four times as much in a month as a monthly sender at the same per-send rate. Whatever your provider reports per campaign has to be multiplied by your send frequency before it belongs in this box. And bounces are not one thing: hard bounces are permanently dead addresses and belong in the losses, while soft bounces are temporary and mostly should not, or you will double-count the same address every month.
The practical consequence of the ceiling is a ranking of the two levers. Halving churn doubles the ceiling. Doubling signups also doubles it, and normally costs a great deal more. Deliverability work, a send frequency people can live with, a welcome sequence that sets accurate expectations and a periodic sunset of addresses that have not opened anything in six months all attack the denominator, and the denominator is the term that decides where the curve flattens.
What people use it for
- Forecasting a list a year out
- Setting a realistic subscriber target
- Modelling the effect of reducing churn
- Deciding whether to invest in acquisition or retention
- Finding the size at which a list stops growing at your current rates
- Explaining why a growth projection and a linear one disagree
Questions
No. It applies your current net rate to every month, so the curve rises for ever. Divide signups by the churn rate to find the ceiling a flat-signup list would actually reach.
350 signups against 2% monthly churn gives 17,500. The projection passes straight through it and keeps going, which is the difference between the two models.
Over twelve months, 8,979 against about 7,692. Over sixty months, roughly 93,000 against about 13,800. The error grows with the horizon.
The panel is a reasonable guide for a year. For anything longer, use the ceiling calculation, and treat the projection as an upper bound rather than a forecast.
Because it turns your signups into a rate and reapplies it. That is right for a list where signups genuinely scale with size, such as one growing mainly by referral.
Net gain per month is linear, gross signups multiplies your flat monthly figure by the months without compounding, and the headline projection compounds. Three questions, three answers.
It varies enough by list, sector and send frequency that a single figure is not much use. Take yours from your own provider’s last few campaigns rather than from a benchmark.
Per month, which means multiplying the per-send figure by how often you send. A weekly sender at 0.3% a send loses about 1.2% a month.
Hard bounces do, because the address is gone. Soft bounces are temporary and counting them monthly double-counts the same subscriber repeatedly.
They are not churn yet but they are the pool it comes from, and they drag on deliverability while they sit there. Track them separately and decide a sunset policy.
Generally yes. Sending to people who never open lowers your engagement signals, which reduces inbox placement for everyone else on the list.
It drops the list size once and lifts the growth rate afterwards, because you stop counting decay on addresses that were never going to respond. The ceiling does not move; the path to it gets cleaner.
Send at a frequency you promised, segment so people get what they signed up for, and make the welcome sequence set accurate expectations. Most unsubscribes are a mismatch between expectation and delivery.
Cutting churn, usually. Halving it doubles the ceiling; doubling signups doubles it too, and costs far more to sustain month after month.
No. A smaller engaged list produces more revenue and better inbox placement than a large indifferent one, and costs less to send to.
How many months the current net rate takes to double the list, under the same compounding assumption. At 5% a month it is 14.2 months.
Not directly. Run the projection to the launch, add the spike to the list size by hand, then run it again from there with whatever the new steady signup rate is.
Yes, and most providers price in bands, so a projection is also a budget forecast. Check where the next price band starts before celebrating the growth.
Because it worked. A re-engagement send prompts a wave of unsubscribes from people who were never going to read anything, which is a one-off correction rather than a trend.
No. The projection runs in your browser and nothing is uploaded.