u/calliope_kekule

Some context so you can judge whether this applies to you. I started a newsletter from nothing in July 2025. Today it has about 22,600 free subscribers in 179 countries and roughly 400 paying members. It has a Bestseller badge.

I write about a fairly serious subject for an audience that is mostly educators and professionals, so adjust for your own niche.

What I do have is a full data export every month, read into a database, so the five things below are what the numbers show rather than what 'felt' true. In descending order of how much they mattered.

1. Notes are where paying members come from. Recommendations are where the free list comes from. Do not confuse the two.
Over twelve months, recommendations from other writers brought me about 15,000 free signups and 77 paying members. That is 5 per 1,000, the worst conversion of any source I have. Notes brought far fewer signups and 121 paying members, the most of any source. The free list is wide and cold. Notes readers already know your voice before they land.
So: post Notes every day, and judge them on paid conversions a week later, never on likes. The Notes that convert for me are first-person positions (I think X, and here is the thing that happened to me that made me think it) and short admissions of being wrong. Over 30 days those get about double the reactions of news-pegged Notes. A Note that just reports a news story does a third of my median

2. Pick one day a week for the paid post and never move it.
Half of my paid upgrades happen on a Wednesday, which is the day the paywalled post goes out. Tuesday carries 2%. The day itself does not matter. What matters is that the same readers see the same wall at the same time every week until the week they are ready, and then they know exactly when the next one is coming.
Two posts a week is my ceiling: one paid, one free. I ran a third weekly post for six months to test that: 25 editions, nearly 400,000 emails sent, 7 paying members came through. It is now gone.

3. Put the paywall where the reader wants to keep reading, never where the "value" starts.
My best-converting paid posts open with the whole story for free and cut mid-stride, at the point where the reader's own curiosity is doing the selling. The worst ones give a free "introduction" and put the useful bit behind the wall, which reads as a toll booth. When someone complains in the comments that the cut was a cliffhanger, that post has usually converted best.

4. Deadlines convert. Nothing else I have tried comes close.
Every real jump in paid I have had came from a date: a price going up on a fixed day, a discount ending at midnight, a cohort closing.
The flip side is renewals. If you sell annual plans in a campaign, a year later they all expire in the same month. Make sure what they bought still exists when the renewal email lands. I stopped unpaywalling old posts for exactly this reason; the archive is now part of the product.

5. Judge every channel by free signups to your Substack, never by views.
I have two TikTok videos with 350,000 views each. The platform they live on sent fewer paying members in a year than Notes did. LinkedIn, with a fraction of that reach, sent about 570 signups in the same year. My highest-engagement topic is also my lowest-converting one; it buys followers, and the topic next to it, with half the reach, buys subscribers. If you only look at the view counter you will keep making the first kind.

Two things I would skip. Reddit as a growth channel: I posted here and in adjacent subs for months and got a handful of signups. It is a good place to learn and a poor place to be found. And the open rate as a vanity number: mine is a 28% median across the last 20 sends, down from a lifetime mean in the mid-thirties, because the list got bigger and colder. It has made no difference to paid.

Happy to answer questions about any of these in the comments.

NB: Claude was used to help me gather this data and also edit parts of this post.

I went from 0 to 22,000 subscribers and 400 paying members in 15 months. Here is what the data says actually worked, and what did nothing.

A new model found flood barriers cut flood risk over 70%, but also caused household flood preparation to fall by about 60%, as people stopped expecting the water.

Climate models suggest that by 2090, particles that seed clouds could rise up to 16% in the High Arctic but fall by up to 31% in the wetter Maritime Arctic.

Only 13% of cancers are caught through screening, while a fifth to half are first found in an emergency department.

A study of 2.3 million older adults found 24 drug 'cascades', where a medicine's side effects get treated with a second prescription. Iron pills leading to laxatives was most common.

In a US trial, teclistamab wiped out cancer completely in 78% of high risk myeloma patients, against 0% on standard treatment, and cut two year progression to 8%.

Hot weather kills off 9.7% of disease carrying mosquitoes, but speeds up the virus in survivors and shifts human behaviour, driving a projected 76% rise in chikungunya cases.

In Uganda, 1,784 children under 2 got yellow fever vaccine at full, half or one fifth strength. The fifth dose protected as well as the full one, stretching scarce supply in an outbreak.

A new material moves protons 6.5 times faster than the standard fuel cell membrane, cutting the energy barrier by more than half.

In a trial of 948 people with stomach cancer in 20 countries, adding durvalumab to chemotherapy before and after surgery cut the risk of dying by 22% versus chemo alone.

Modelling over 16,000 groundwater samples, researchers found wells near land vulnerable to shale gas spills were three times more likely to carry deep drilling fluid chemicals.

A pill nearly halved deaths from head injury In a Swedish led trial in a low income hospital, 20% given the drug Salovum died within 30 days, against 39% on standard care. Most patients were young men, average age 33.

Modelling projects drylands will cover about 40% of all land on Earth by 2100 under a high emissions path, as CO2 changes how much water plants and soil release.

A Czech trial of 558 people with dangerous lung clots found feeding clot dissolving drugs straight into the lung artery cut deaths and repeat clots to under 1%, against nearly 7% on blood thinners alone.

A trial of 6,238 heart attack survivors in France found stopping beta blockers about as safe as staying on them: 17.2% who stopped had a problem, versus 15.9% who stayed.

A survey of 3,751 Syrian and Iraqi refugees found that drought made war's mental toll worse.

In a 70 person US safety trial, Kylo 11 lowered lipoprotein(a), a heart risk marker diet can't touch, by up to 97% over 48 weeks. Over half had side effects, none serious.

Across 16 hospitals in sub-Saharan Africa, a new trial covering 134,630 women cut the odds of early newborn death by 22%.

In a trial of 393 patients in the United States, the highest dose cut eczema skin symptoms by 61%, against 31% on a placebo, after 16 weeks.

In a trial of 20 patients in China, those injected with lab grown heart muscle cells walked further and had better blood flow than bypass surgery alone. However, there was an increase in arrhythmia that would need to be addressed fully in further studies.