# How to time an exam: start, finish, reading time and extra time Source: https://spolvero.design/articles/how-to-time-an-exam/ Updated: 2026-10-11 Tool: https://spolvero.design/tools/timers/exam-clock/ > Show candidates three things: the start time, the finish time and the time remaining. Start the clock when the paper actually begins, not at the scheduled time, and work every other time out from that moment. Run reading time as its own countdown before writing time. For extra time, add the allowance to the finish time: 25% extra on a two-hour paper is 30 minutes. Announce the time remaining at the points your exam board sets. Most timing problems in an exam room come from arithmetic done in a hurry. The paper starts four minutes late, someone works out a new finish time in their head, and the board and the clock disagree for the next two hours. The way to avoid it is to make one moment, the actual start, the source of every other time. ## What candidates need to see 1. **The start time**, as it happened. 2. **The finish time**, which they plan against. "I need to be on question 4 by ten past" is a thought about the finish time, not about minutes remaining. 3. **The time remaining**, which the invigilator needs for announcements and nervous candidates like to check. A wall clock gives only the current time and leaves each candidate to subtract. A countdown alone gives no finish time to plan against. Show all three. ## Start when the paper starts Whatever the timetable says, the duration runs from the moment candidates are told to begin. If a two-hour paper scheduled for 9:00 begins at 9:04, it ends at 11:04. The [exam clock](/tools/timers/exam-clock/) works this way. You set the length, press start when the paper begins, and it writes the start and finish times from that moment, so what is on screen always agrees with itself. Press F for fullscreen and project it; the fullscreen view is the clock alone, with no ads. Add a label, such as the room or the paper, if several rooms are running at once. ## Reading time Some papers give a reading period before writing starts. It is not taken out of the writing time. Run it as its own countdown, clearly labelled, and begin the writing time at full length when it ends. In the exam clock, turn on a reading period and it counts that first, labelled as reading time, then moves into writing time by itself. Candidates can see which phase they are in without asking. ## Extra time Extra time is a percentage of the paper's length, most often 25%. Work it out before the day, not during the paper. | Paper length | 25% extra | New total | | --- | --- | --- | | 45 minutes | 11 min 15 s | 56 min 15 s | | 1 hour | 15 min | 1 h 15 min | | 1 hour 30 | 22 min 30 s | 1 h 52 min 30 s | | 2 hours | 30 min | 2 h 30 min | | 2 hours 30 | 37 min 30 s | 3 h 7 min 30 s | | 3 hours | 45 min | 3 h 45 min | If the whole room has the allowance, set the clock to the new total. If one candidate has it, write that candidate's finish time on a card on their desk, and run a second clock for them in another browser tab or on another device. One clock shows one finish time. If something interrupts the paper, such as a fire alarm or a candidate taken ill, note the time lost and add it back. The exam clock lets you add minutes while it runs, and the finish time on screen moves with it. ## Announcements Exam boards set their own rules for when invigilators speak, and those rules come first. Where you have a choice, as in a class test or a mock, two announcements are enough: one at thirty minutes remaining and one at five. More than that breaks concentration more than it helps. ## Check the room before anyone sits down - Project the clock and **walk to the furthest desk**. If you cannot read the finish time from there, enlarge it before the candidates arrive. - **Plug the laptop in** and close anything that might show a notification over the clock. - The page asks the browser to keep the screen awake while the clock runs. The time itself comes from the system clock, so even if the machine did sleep, the time remaining would be right when it woke. ## Mock exams at home Everything above applies to one person at a kitchen table. Use the real duration. Put the clock where you can see it without picking up a phone. Stop when it stops. Pacing is a skill, and the only way to practise it is against a real finish time. To know what you should have done by each point, work out a plan first. The [exam time calculator](/tools/calculators/exam-time-calculator/) shares the time out by marks and gives each section a finish-by time; [minutes per mark](/articles/minutes-per-mark-exam-time/) explains the arithmetic, and [how to split a 3-hour exam](/articles/how-to-split-a-3-hour-exam/) works it through for two CBSE papers. For timing lessons and group work, where the clock needs to be friendlier, see [classroom activity timings](/articles/classroom-activity-timings/). ## Questions ### What should be displayed on the board during an exam? The start time, the finish time and a clock every candidate can see, along with the centre number and paper details your board requires. Candidates plan against the finish time, and invigilators use the time remaining for announcements, so showing both removes most questions from the floor. ### How much is 25% extra time? A quarter of the paper's length: 11 minutes 15 seconds on 45 minutes, 15 minutes on an hour, 22 minutes 30 seconds on 90 minutes, 30 minutes on two hours, and 45 minutes on three hours. Add it to the finish time and write the new finish time down for that candidate. ### What happens if an exam starts late? The full duration still applies. Start the clock when candidates are told to begin, and take the finish time from that moment. Do not keep the scheduled finish time, because that would shorten the paper. ### Is reading time part of the exam time? Where a paper has a reading period, it comes before the writing time and is not taken out of it. Candidates may read but not write answers. Time it as a separate countdown so that the writing time starts at its full length. ### How do I time a mock exam at home? Use the real duration, put a clock with the finish time where you can see it without touching a phone, and stop when it ends. Practising against the finish time, not only a countdown, is what builds pacing for the real paper.