Set the ideal study-to-break ratio for focus.
The right focus-to-break ratio depends on cognitive load. Light reading sustains longer blocks, so the focus period is stretched by about twenty percent, while genuinely new difficult material burns attention faster and the block is cut by a quarter. Adjusting the period first and then fitting whole cycles into the available time gives a plan where every block finishes rather than being cut short.
Adjusted focus period
Recommended focus = base focus period x difficulty factor, where light is 1.2, moderate 1.0 and heavy 0.75
Session structure
Cycles = floor(total minutes / (adjusted focus + break)); ratio = adjusted focus / break
It is a good default, especially for starting tasks you are avoiding. For deep work many people do better with fifty to ninety minute blocks, since twenty-five minutes can interrupt flow just as it starts.
Something genuinely different — standing, walking, looking into the distance. Switching to a phone keeps the same cognitive and visual load, so it restores much less.