How to use the online timer
Fifty minutes of work against a ten-minute break suits tasks that take real time to get into: writing, drawing, coding, working through a complicated set of accounts. In a twenty-five-minute block, the first five minutes are often spent reassembling where you got to, which is a fifth of the block gone; over fifty minutes that overhead is proportionally much smaller and there is room to reach the state where the work carries itself.
The longer block asks more of you in the middle. Fifty minutes is long enough for a wandering thought to turn into ten minutes of browsing without much resistance, so deciding the specific outcome before starting matters more here than it does with the shorter split. Vaguely defined work does not survive fifty minutes of solitude with an internet connection.
Ten minutes of break is enough to leave the desk properly, which the shorter version never quite is. Four rounds of this comes to four hours including breaks, so it maps onto a morning and part of an afternoon rather than a whole day. Somewhere after the third round, most people find the blocks getting noticeably harder, and that is usually the point to take a longer break rather than starting a fourth out of stubbornness.
Common questions
When is fifty minutes better than twenty-five?
For work that takes time to get into, such as writing, drawing or complex analysis. In a short block, the first five minutes are often spent reassembling where you left off.
Is it harder to stay focused for fifty minutes?
Generally yes, so decide the specific outcome before starting. Vaguely defined work rarely survives fifty minutes alone with an internet connection.