Kit vs Substack: A Monthly Plan or a Share of Revenue

The short answer: if you are starting a paid newsletter with no budget and want readers to find you inside a reading app, Substack is the simpler start: its pages show no plan to choose, and writers keep 90% of their revenue minus card fees, per its going-paid page. Once that 10% share costs more each month than a Kit plan for your list, or once you sell courses and products through automated sequences, Kit is the better home (Kit sequences).

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Kit's pricing page and help centre showed a security check instead of content on 26 October 2026, so Kit's plan prices are missing here. The comparison below uses Kit's developer documentation and Substack's own pages, and it shows how to finish the sum with Kit's figure once you have it.

The sums to do before you choose:

1. Turn the 10% into money. Substack's own example is 1,000 subscribers paying $5 a month (going-paid page). That is 1,000 x $5 = $5,000 a month, of which 10% is $500 a month, or $6,000 a year, before card fees.
2. Find your break-even. Take Kit's monthly price for your list size from its pricing page and divide it by 0.10. For example, at a plan price of $100 a month, a round figure for the arithmetic and not Kit's quoted price, the break-even is $100 / 0.10 = $1,000 of paid revenue a month. Below it Substack's share is cheaper; above it, the plan is.
3. Decide what success means before you move. Paid conversion rate from free readers, or revenue per subscriber. Take the figure from your current tool so the new one is measured against it.

Who holds what

From Kit's developer pages on posts, the Creator Profile, purchases and the MCP server, and from Substack's homepage and going-paid page. Substack's support centre also returned a security check on 26 October 2026, so its fee and export articles could not be read.

What separates them

The meter moves with your success on one side

Substack's charge, as its going-paid page describes it, is a share of what readers pay, so it grows with every paying reader. A plan fee works the other way: it is due in a month with no revenue and stays flat as revenue grows. Neither is better in general. Early on, a share is kind to you; later, a flat fee usually is, and the break-even sum above tells you which side of that line you are on.

A reading app against a business toolkit

Substack's homepage is a feed of posts from writers, with a subscriptions list, chat and an explore tab (Substack). Readers who already use the app can find you there. Kit's documentation is a toolkit for running a creator business: sequences that send in order on set days, broadcasts targeted by tag or segment, purchases synced from your store, and an app store for tools built on Kit (App Store overview).

What you can automate

On Kit, a purchase recorded from your store lands on the buyer's subscriber record, and sequences and tags decide what that person receives next, without anyone opening the account (purchases reference). The Substack pages read for this comparison describe free and paid posts, chat and payments, and no automated sequences or API. If the newsletter is one part of a business with a course, a product or coaching, that gap decides it.

What each costs you

Substack, from its going-paid page, checked on 26 October 2026: writers keep 90% of revenue minus card fees, so Substack's share is 10% of paid revenue. The pages read show no monthly plan.

Kit: its pricing page could not be read on 26 October 2026. Enter your list size there, then put the monthly figure into the break-even sum at the top.

One step only Kit documents: an agent drafts next week's issue

Kit's MCP server, on its paid Creator and Creator Pro plans, exposes the v4 API to Claude, ChatGPT, Cursor and other clients after an OAuth sign-in (Kit MCP). Ask the assistant to pull the stats for your last ten broadcasts, name the three subjects with the highest click rates, and draft next week's issue in that direction. In the API, a broadcast saved without a send time stays a draft, and it can be marked for the web as well (broadcast reference). The editor reads the draft, fixes facts and voice, and schedules it; Kit says sending always needs explicit confirmation in supporting clients. Substack's pages document no equivalent, so on Substack this step is done by hand.

Start for nothing

The cheapest test is the one you run on paper. List your expected paying readers at three points, now, in six months and in a year, and put each into the 10% sum and the break-even from the going-paid page figures. If the share stays below a Kit plan all year, start on Substack. If it crosses within months, start on Kit and avoid a migration later.

Substack's revenue calculator shows what you could earn per month at a chosen price and audience (going-paid page). A calculator built by the party that takes a share shows the earnings, not the share. Work the 10% out in currency yourself, as above.

Choose Kit if your job is

• Selling courses, products or coaching through automated sequences next to the newsletter.
• Paying a flat plan fee once paid revenue has passed the break-even.
• Handing routine work to an AI assistant through Kit's MCP server.

Choose Substack if your job is

• Starting a paid newsletter whose cost follows paid revenue rather than a monthly plan.
• Being found by readers inside Substack's app.
• Writing posts and nothing else, with no automation to maintain.

FAQ

How much of my paid revenue does Substack keep?

Its going-paid page says writers keep 90% of their revenue minus credit card fees, which leaves 10% with Substack (going-paid page).

Can Kit publish posts on the web, as Substack does?

Yes. A broadcast can be published to the web, and Kit's posts carry a public address and a flag for paid content (broadcast reference, posts reference).

Do I keep my list if I leave Substack?

Substack's homepage says you always own your intellectual property, mailing list and subscriber payments (Substack). Its export steps sit in its support centre, which could not be read for this page.