Ask around and you will get numbers. Ten, twenty, forty-five, two twenty-minute sittings a day, each delivered with the confidence of a rule. They are not rules. They are the length that suited the person saying it.
People who sit regularly tend to land somewhere less satisfying: the length you will actually do, most days, beats the length you admire. A five-minute sitting that happens is a sitting, not a compromised twenty.
What the lengths feel like
Descriptions, not prescriptions. People vary enormously and so do days.
Three to five minutes. Long enough to arrive, short enough that nothing has time to get difficult. Dismissed as barely a sitting by people who sit longer, and named as the only reason they still sit at all by people who are busy. This is the length that survives a bad week.
Ten minutes. Where most people report the initial fidget passing and something quieter turning up underneath. Popular as a default for that reason.
Twenty minutes. Long enough that the sitting stops being a thing you are getting through. Also long enough that a restless day is properly felt.
Thirty to forty-five. Described as a different animal, not more of the same. Several distinct weathers pass through a sitting that long. Common among people with an established practice, often not daily.
Open-ended. No fixed end at all, until you decide to stop. Some people find this freeing. Others find that without a decided length, should I stop now? becomes the entire sitting.
Where twenty came from
The number turns up everywhere, and it helps to know it is a convention with a history rather than a finding.
Transcendental Meditation popularised twenty minutes twice daily as it spread through the West from the late 1950s, and that shape carried well beyond the practice it came from. Formal sittings in Zen centres tend to run twenty-five to forty minutes, set largely by how long a group can sit before people need to move. Secular courses land near twenty because it fits a recording, a lunch break and a person's patience at once.
None of that makes twenty wrong. It makes it a default that came from somewhere, and defaults that came from somewhere are the ones to hold loosely.
Why deciding beforehand matters
Whatever the number, picking it in advance does something picking it mid-sitting cannot.
A mind twelve minutes into a quiet room is a poor judge of elapsed time and a persuasive negotiator. If the length is still open, it becomes something to think about, and thinking about how much longer to sit is arithmetic.
Deciding beforehand also means the sitting has one fewer thing in it. That is most of what a timer buys you.
One long sitting, or two short ones
People do both and describe the difference instead of a winner.
Two shorter sittings put the practice into the day twice, which changes the day more than a single block does for some people. There is a second point at which you stop. The cost is that the settling happens twice, and if settling is the slow part, half your practice is settling.
One longer sitting has a middle. Everything past the first stretch is a different kind of time, and people who value that name it as the reason they sit long at all. The cost is scheduling. A forty-minute block is a thing a day can refuse to contain.
The common compromise: a small daily sitting that never moves, and a longer one when the day offers room.
The five-minute day
There will be days with five minutes in them and no more.
The case for sitting anyway has nothing to do with five minutes accomplishing what twenty does. The practice stays a thing you do, and tomorrow is not a restart. A short sitting on a full day is a placeholder, and placeholders are useful.
The case against is that a token sitting can become a way of not really sitting, done to keep a count intact. That is a real failure mode. The tell is whether you are watching a number.
Getting longer
Almost nobody who sits for forty minutes started there, and very few got there by scheduling it.
The usual account runs the other way. The length stops being the interesting part, the current one starts to feel short, and one day you set a bigger number without much ceremony.
If a longer sitting feels like an obligation, that is information. There is no prize at the top.
The practical answer
Pick something small enough that you are confident you will do it tomorrow as well. Sit that for a while. Change it when it starts to feel short, not out of obligation.
Unglamorous, and it is the whole method.
