Time math
How long is a semester?
A college semester in the United States is usually about 15 weeks of classes plus one week of final exams. That is about 16 weeks, or four months. The length differs by school: federal student aid rules count any term of 14 to 21 weeks of classes and exams as a semester.
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Reviewed by Mohammed Raqeeb
The answer
How many weeks are in a semester?
A semester is about 16 weeks long at most US colleges: 15 weeks of classes + 1 week of final exams = 16 weeks. This page is about colleges and universities in the United States. No law sets one length, so each school chooses its own.
Two official sources give the usual figure and the range. The federal definition of a credit hour is written for about 15 weeks of classes. The Federal Student Aid Handbook, the rule book colleges follow when they pay out student aid, says a semester has between 14 and 21 weeks of instruction. A week of instruction is a week with classes or exams in it.
The table shows the fall 2026 semester at three large universities, taken from each school’s own calendar. Each one is between 115 and 117 days from the first class to the last exam, which is 16 weeks and a few days. Arizona State describes its full semester as 15 weeks plus final exams.
| University | First class | Last exam | Length |
|---|---|---|---|
| Arizona State | 16 weeks, 3 days115 days | ||
| Ohio State | 16 weeks, 3 days115 days | ||
| Penn State | 16 weeks, 5 days117 days |
Dates for fall 2026 from the calendars of Arizona State University, The Ohio State University and Penn State. The length runs from the first class to the last final exam, with both of those days counted. The days off for Thanksgiving are inside it.
In months
How long is a semester in months?
A semester is about four months long. A fall semester usually runs from late August to the middle of December. A spring semester usually runs from January to early May. At Penn State, for example, spring classes start on and the last final exam is on .
Two semesters make a school year. Federal rules for student aid ask for a school year of at least 30 weeks of instruction, which is two semesters of 15 weeks. A summer term may be shorter than a semester.
Some classes last only half a semester. Arizona State, for example, runs two sessions of 7.5 weeks inside each semester.
Three kinds of term
Semester vs quarter vs trimester
A semester is longer than a quarter. A college on semesters has two main terms in a school year, fall and spring. A college on quarters has three, fall, winter and spring, and each one is shorter.
A quarter has between 9 and 13 weeks of instruction in the same federal handbook. At UCLA, the fall 2026 quarter is 79 days from the first class to the last exam, which is 11 weeks and 2 days. At the University of Washington it is 80 days.
A trimester calendar has three terms in a year: fall, spring and summer. The handbook gives a trimester the same length as a semester, and two of the three make a school year.
| What is compared | Semester | Trimester | Quarter |
|---|---|---|---|
| Weeks in a termOf instruction | 14 to 21 | 14 to 21 | 9 to 13 |
| Terms in a yearWith summer | 3 | 3 | 4 |
| Terms in a school year | 2 | 2 | 3 |
| Full-time credits a termAt least | 12 | 12 | 12 |
| Credits in a school yearAt least | 24 | 24 | 36 |
From the Federal Student Aid Handbook and federal regulations. A quarter credit is a smaller unit than a semester credit. Breaks do not count as weeks of instruction, and a week of final exams does.
Your own term
Count the weeks in your own semester.
The counter takes the first day of your classes and the last day of your final exams, and gives the weeks and days between them. While your term is running, it also says which week of the term today is. Add your credits to see the hours a week they ask for.
An example to start from: the fall term at Arizona State University, to . Change both dates to your own. They are on your school’s academic calendar.
Use the minus and plus, or the arrow keys. The counter takes from 1 to 24 credits.
From the first class to the last exam
16 weeks and 3 days
115 days, from to , with both of those days counted.
- Days in all
- 115
- Monday to Friday
- 82
- Saturdays and Sundays
- 33
What your credits ask for each week
45 hours
15 hours in class and 30 hours of reading, homework and study, for 15 credits. Over 15 weeks of classes that is 675 hours.
My term is 16 weeks and 3 days long: 115 days, from to .
The hours follow the federal definition of a credit: 1 hour in class and at least 2 hours of other work each week. Your own courses may ask for more or less. Nothing you enter leaves this page.
In hours
How many hours a week is a semester of classes?
A semester of 15 credits asks for about 45 hours a week. The federal definition of a credit hour is 1 hour in class and at least 2 hours of other work each week, for about 15 weeks. Other work means reading, homework and study. So one credit is 3 hours a week, and 15 credits × 3 hours = 45 hours.
That is more than a work week of 40 hours. Over 15 weeks of classes it adds up to 675 hours. Full time for student aid starts at 12 credits a term, which is 36 hours a week by the same sum.
The definition is what a college plans a credit around. It does not measure what students really do, and one hard course can take more than its share.
| Credits | In class | Other work | A week | In 15 weeks |
|---|---|---|---|---|
| 3One course | 3 | 6 | 9 | 135 |
| 6 | 6 | 12 | 18 | 270 |
| 9 | 9 | 18 | 27 | 405 |
| 12Full time | 12 | 24 | 36 | 540 |
| 15 | 15 | 30 | 45 | 675 |
| 18 | 18 | 36 | 54 | 810 |
All figures are hours. The first three columns are hours a week. To spread the study hours for one exam over the days you have, use the study planner. What to do in those hours is on how to study effectively.
High school
How long is a high school semester?
A high school semester is about 18 weeks at a school that splits its year into two halves. A high school year is longer than a college year. In a table from the National Center for Education Statistics, 28 states and the District of Columbia set a school year of at least 180 days of class, as of 2020.
Half of 180 days is 90 school days. A school week has 5 days, so 90 ÷ 5 = 18 weeks of class. The other states set a different number or leave it to each district, so check your own school’s calendar.
Your own hours
How to see where a semester’s hours go.
The hours in the table are a plan. To see what you really spend, write down each day what you did for your classes and for how long: a lecture, an hour of reading, two hours on a problem set. Doing this every day is called time journaling. One week of it shows whether the hours you planned are the hours you gave. For the rest of the year, see how many weeks are in a year.
A semester’s study hours come in many short stretches, and by the end of a week it is hard to say how many there were.
It helps to have the hours counted from a few words you write or say about your day, so there is no timer to start before each class. Most journaling apps ask how the day felt. They do not add up the hours that went to lectures, reading and homework.
One app built for this is Think in Numbers, a smart journaling app with time tracking built in.
You write or say your day in your own words, as it happens or all at once. The app reads what you wrote and counts the hours that went to each part of it: classes, study, sleep, work, your phone, and the time you never mentioned (shown as unaccounted). Then it shows those hours over days and weeks. So you can set your real study hours beside the hours your credits ask for, week by week.
1. You write your day
2. It counts the hours
- Study0m
- Classes0m
- Sleep0m
- Unaccounted24h
3. It shows your week
Study this week: 0m
On 6 of 7 days. The gap is the day without it.
An example day and week.
For iPhone and Android. Try it on your own day before you pay.
Sources
Where the figures come from.
- U.S. Department of Education, Federal Student Aid (read ). 2026-2027 Federal Student Aid Handbook, Volume 3, Chapter 1: Academic Years, Academic Calendars, Payment Periods, and Disbursements.
- Code of Federal Regulations, U.S. Government Publishing Office (read ). 34 CFR 668.3: Academic year.
- Code of Federal Regulations, U.S. Government Publishing Office (read ). 34 CFR 600.2: Definitions (credit hour).
- Arizona State University, University Registrar Services (read ). Academic calendar.
- The Ohio State University, University Registrar (read ). Academic Calendar: 5-year view (2023-2028).
- Penn State, Office of the University Registrar (read ). 2026-27 Academic Calendar.
- UCLA Registrar’s Office (read ). Annual Academic Calendar.
- University of Washington, Office of the University Registrar (read ). 2026-2027 Academic Calendar.
- National Center for Education Statistics, State Education Practices (read ). Table 1.1. Minimum number of instructional days and hours in the school year, by state: 2020.
Keep reading.
- Time journalingThe method: write or say your day in your own words, then see it as hours.
- Weeks in a year52 weeks and 1 day, or 2 days in a leap year, with work weeks and the years whose calendars show a week 53.
- Study plannerYour exam date in, hours a day and a calendar out.
- How to study effectivelyThe methods with the strongest evidence, and a study planner.
- Where did my week go? calculatorEnter a typical day and see your week accounted and unaccounted.
Questions
Questions people ask.
How many weeks are in a semester?
A semester at most US colleges has about 15 weeks of classes and one week of final exams, about 16 weeks in all. Federal student aid rules count a term of 14 to 21 weeks of classes and exams as a semester.
How many months is a semester?
A semester is about four months long. A fall semester usually runs from late August to the middle of December, and a spring semester from January to early May.
How many semesters are in a year?
Two semesters make a school year: fall and spring. Many colleges also run a shorter summer term. A college on quarters has three quarters in a school year: fall, winter and spring.
How long is a quarter in college?
A college quarter has between 9 and 13 weeks of classes and exams under federal student aid rules. At UCLA, the fall 2026 quarter is 11 weeks and 2 days from the first class to the last exam.
How many hours a week is 15 credits?
Fifteen credits are about 45 hours a week: 15 hours in class and 30 hours of reading, homework and study. That follows the federal definition of a credit hour. Your own courses may ask for more or less.
How do I keep track of my study hours over a semester?
A paper planner or a notes app is enough: each evening, write down what you studied and for how long, and add it up on Sunday. It helps if the hours get added up for you, so you can set one week beside the next. One app built for this is Think in Numbers, a smart journaling app with time tracking built in. Think in Numbers counts your study hours from what you write or say about each day, and shows them week by week.
Try it on my day.
Write today down in your own words, and see where the hours went.
For iPhone and Android. Try it on your own day before you pay.