Ask a sixth form common room how many hours everyone revises and you'll hear some impressive numbers. Ten-hour days. All-nighters. Library shifts that sound like factory work. Then results come out, and the students at the top of the list are rarely the ones who claimed the biggest numbers. I got top A-level grades, survived a medical degree, and can tell you why: hours are an input, and exams pay for output.
The honest numbers, stage by stage
In Year 12 term time, one to one and a half hours per subject per week of genuine consolidation on top of homework is enough: how many hours revision a level turning the week's lessons into flashcards, blurting new topics, doing a few exam questions. In Year 13, push toward two hours per subject: one consolidating new content, one retrieving older content so it doesn't decay. In the holidays, 1.5 to 2 focused hours a day, five days a week. In exam season, four to six hours a day in proper blocks, and almost never more, a level revision hours
per day because studies of demanding mental work keep finding the same ceiling of roughly four to five genuinely focused hours a day, even in elite performers.
Why the ten-hour day is a myth
A teenager announcing a ten-hour revision day is usually describing about four hours of real work stretched across ten hours of low-grade guilt, minus the sleep that consolidates memory, how many hours should i revise plus exhaustion carried into tomorrow. Sleep isn't a break from revision. Overnight consolidation is when the day's work gets written into long-term memory, which makes latenight cramming a machine for undoing its own effort.
What to do with the hours instead
Quality multiplies time. One focused hour of active recall (blurting, flashcards, past paper questions) beats three passive hours of re-reading notes, which is why the question "how long should I revise" matters less than "doing what". Work in blocks of 45 to 60 minutes with real breaks. Decide the topic before the session starts, because choosing what to revise during revision time is how an hour disappears. Mix subjects across the day rather than binging one. Put the phone in another room, since most six-hour days contain ninety phone-minutes nobody
counted. And weight everything toward your weakest topics, where the recoverable marks actually live.