Article
Why twenty five minutes, and why you cannot change it
There is no evidence that twenty five minutes is the right length for a session. Untimer uses it anyway, and does not let you change it. Here is why both of those are true at once.
Every session in Untimer is twenty five minutes. Every set is four sessions. There is no setting for either, on any screen, on any device. The breaks are yours to choose, and so is the end of your working day. The session is fixed.
People ask about this more than anything else, usually as a request. Could I have thirty. Could I have fifty two, because I read that somewhere. Could I have a short one for the days when starting is hard. The answer is no, and this article explains why a product that asks so little of you is so firm about one number.
There is no magic number
Twenty five minutes is not a scientific finding. Nobody has shown that the mind can concentrate for about that long and then stops. It is a common length for focus sessions, and that is all it is.
We looked at the research. The best controlled study we found on fixed break schedules, by Biwer and colleagues in 2023, compared two fixed schedules with breaks taken whenever people felt like it, and found no difference in how much work got done. People on a fixed schedule did say they felt more concentrated and less tired, which is worth something. The two schedules were twenty four minutes on and six off, and twelve on and three off, and they came out about the same. The structure seemed to matter. The exact number did not.
So we will not tell you that twenty five minutes is right. We tell you it is fixed, which is a different thing.
Fixed is easier to start
Untimer is built for people who find starting hard. Every choice placed between you and the start is a place to stall, and a duration setting is a choice placed exactly there. Would twenty be better today. Is thirty too much. Should this one be short because it is only email. That conversation is the thing focus is supposed to replace.
Early versions of the glass let you choose a length as you wound it, and it changed how the wind felt. People watched the number instead of feeling the spring. So we removed the choice. You wind the glass, it is twenty five minutes, and the only decision left is whether to begin.
The founder’s own history says the same thing. Thousands of recorded sessions over several years, all the same length, with the setting available the whole time and never changed once. A number that is never changed does not need a control, and a control invites fiddling with something you meant to set once.
The hard days
The honest objection is about starting. On some days twenty five minutes is too tall a door, and a two minute session would get you through it. We think that is true, and the answer is still not a duration setting.
The answer is that stopping early is fine. Wind the glass, work for four minutes, press Stop. The sand pours back to the bottom, nothing anywhere treats it as a failure, and the app says nothing at all: the four minutes count for nothing, and so does the twenty five you did not do. You got through the door, which was the hard part, and the door is the same height tomorrow.
The long ones
The other objection is about deep work. Twenty five minutes is short for a task that takes twenty minutes to get into, and a bell in the middle of real progress is unwelcome. The sound at zero is soft on purpose, and the break it announces waits for you. Letting a session run past its end, calmly, is on the list of things still being built, because the record has to stay accurate about it and that takes care.
Until then the session ends at zero, the sound is soft, and the break waits. Finish the thought. Nothing starts without you.
The set is four, and you can correct it
The set works the same way. After four completed sessions the long break comes round, and four is fixed too. What you can do is tell Untimer where you really are. Sessions run somewhere else, a long break taken away from the app, a set already half done when you opened it: counts drift for ordinary reasons, and a count you cannot correct is a count you stop believing. One control says I am actually at two, and the next long break starts the set again from nothing.
What is yours to set
Nothing about the timer. A session is twenty five minutes, a break is five, a long break is twenty five, and a set is four. There is no control for any of them and there is not going to be one.
A break is the most it takes, and you owe none of it: End the break stops one the moment you have had enough, and nothing is counted against you for it. So a three minute break needs no setting to reach.
The one thing that is yours is whether your working day has an end, and when. We think that is the one that matters: a set time to stop, so the day ends. It is not a length of anything, and only you know it.
We would rather say all of this plainly here than hide it behind a gear icon. A screen full of numbers to adjust is somewhere to go instead of starting, and starting is the hard part.