How often should a one-person business post?

The right frequency is the one you can still keep in the third month. Everything above that is borrowed from a future week.

The short answer

Work out the minutes you can genuinely give this each week, then divide by the minutes one good post takes. That is your ceiling, not your ambition.
Choose a cadence below the ceiling so a bad week does not break it.
Hold it for a quarter before changing it. Two weeks of data tells you nothing.
Judge it by replies, saves and clicks - not by whether you hit the number.
Batch the writing, spread the publishing. They are different jobs and only one of them needs daily attention.

Why more is often worse

Posting frequency has a cost that does not appear in any dashboard: the attention you are not giving to the work you sell. A one-person business that posts three times a day is usually a business that has stopped shipping.

There is also a reader cost. Every weak post teaches someone that your posts are weak, and that lesson outlasts the good one you publish tomorrow.

Picking your number

Time yourself writing one post you are happy with, end to end. Use the real number, including the staring.
Decide the weekly minutes you will protect for this. Be pessimistic.
Divide, then round down to a cadence you could keep during your busiest month.
Write the cadence down with a review date one quarter away.
At the review, look at what people replied to. Do more of that, not more of everything.

One platform, done properly

A cadence is per platform, not in total. Three posts a week on one platform is a manageable habit; three a week across four platforms is twelve posts and a second job.

Pick the one where the people who buy from you already are, hold your cadence there for a quarter, and only then consider a second. When you add one, halve the ambition rather than doubling the hours.

Signs the cadence is wrong

You are posting to fill a slot rather than because you have something. Drop a day.
You have not shipped anything in the product for a fortnight. The posting is eating the business.
Replies have gone quiet while volume went up. That is a signal about quality, not frequency.
You are drafting at midnight. The cadence is above your ceiling.

The free tool for this

There is no calculator that answers this one honestly, so here is the free set: eight calculators for rates, quotes, invoices, splits, prices and fees. They run in the page and send nothing anywhere.

If you would rather not build it yourself

Content Engine plans ninety days at a cadence you choose, with skeletons and a repurpose map, so the question of what to post on Thursday is answered before Thursday. 90-Day Content Calendar & Batch Planner - Notion + Excel (Content Engine) is $17. See it on the shop, and there is a plain page about it here: what it holds.

Questions people actually ask

Is once a week enough to be found?

For a one-person shop, a consistent weekly post plus pages that answer search questions will usually do more than daily posting alone. Search pages keep working while you sleep.

Should I post the same thing on every platform?

Reuse the idea, rewrite the post. Pick one platform to do properly before you add a second.