Time math
What is a 9/80 work schedule?
A 9/80 work schedule is 80 hours of work done in 9 days instead of 10, over two weeks. You work eight 9-hour days and one 8-hour day, and you get one extra day off every second week. The sum is 8 × 9 + 8 = 80.
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Reviewed by Mohammed Raqeeb
The two weeks
How does a 9/80 work schedule work?
A 9/80 work schedule puts two weeks of full-time hours into nine working days. In the first week you work four 9-hour days and one 8-hour day. In the second week you work four 9-hour days and take the fifth day off.
The table shows the two weeks with Friday as the short day and the day off. That is how Sandia National Laboratories describes its own: every other Friday off. An employer can use another day of the week.
| Day | Week one | Week two |
|---|---|---|
| Monday | 9 hours | 9 hours |
| Tuesday | 9 hours | 9 hours |
| Wednesday | 9 hours | 9 hours |
| Thursday | 9 hours | 9 hours |
| Friday | 8 hours | Day off |
| The weekMonday to Friday | 44 hours | 36 hours |
The two weeks add up to 44 + 36 = 80 hours, the same as two usual weeks of 40. Eight of the days are one hour longer than a usual 8-hour day. Those 8 extra hours are the hours of the day off.
For example, a 9-hour day can run from 8 AM to 6 PM with an hour for lunch, and the short Friday from 8 AM to 5 PM.
Side by side
How does 9/80 compare with a usual week and four 10-hour days?
A 9/80 schedule is in between the usual week of five 8-hour days and a week of four 10-hour days, which is often written 4/10. All three come to 80 hours in two weeks, and to 2,080 hours in a year of 52 weeks. They differ in the length of a day and in the extra days off.
| Schedule | Days worked in two weeks | Extra days off a year |
|---|---|---|
| The usual week8 hours a day | 10 | None |
| 9/809 hours a day, and 8 on one day | 9 | 26 |
| 4/1010 hours a day | 8 | 52 |
The 26 extra days off are one in every two weeks: 52 ÷ 2. The page on working hours in a year takes holidays and vacation out of the 2,080.
Your days off
See your 9/80 days off on a calendar.
Choose one of your days off. The calendar marks that day and every second week after it, and shows which days are the short ones.
An example, as if your day off were . Any day off on your schedule, within a year of today. The others are counted from it, two weeks apart.
- A day off, in the example
- A short day, in the example
- 8 hours, not 9
Days off in the three months shown, in the example
5
Every second Friday, from to . Each one makes a weekend of three days.
The example’s days off, in order
5 days off, ready to paste into your own calendar.
One day off in every two weeks of 80 hours. Public holidays are not in it. Nothing you enter leaves this page.
The workweek
How does overtime work on a 9/80 schedule?
Overtime on a 9/80 schedule depends on where the employer starts the workweek. Under US federal wage law, overtime pay starts after 40 hours in a workweek for covered employees who are not exempt, and hours cannot be averaged over two weeks (the Wage and Hour Division). Counted from Monday to Sunday, a 9/80 schedule has 44 hours in one week and 36 in the next.
The same law lets a workweek begin on any day and at any hour, as long as it stays fixed. So some employers start the workweek in the middle of the 8-hour day. The first 4 hours of that Friday end one workweek, and the last 4 begin the next.
| Workweek | What is in it | Hours |
|---|---|---|
| Friday noon to Friday noon | Short Friday afternoon (4), Monday to Thursday (36), Friday off | 40 |
| The week after | Friday off, Monday to Thursday (36), short Friday morning (4) | 40 |
The State of California sets up its own 9/80 schedules this way. Its policy says the work week “begins and ends four hours into” the short day, so that every work week has 40 hours (the California Department of Human Resources). Federal agencies follow their own rules. For their full-time staff, overtime is the hours worked beyond the fixed schedule itself (the Office of Personnel Management).
This section describes how employers set the schedule up. It is information, not legal advice.
Who uses it
Who uses a 9/80 work schedule?
A 9/80 work schedule is used by government agencies and by other employers, under more than one name. Three publish their rules:
- Federal agencies. In its handbook for them, the Office of Personnel Management calls it the 5/4-9 compressed plan. Each agency decides whether to offer it.
- The State of California, which calls it a 9/8/80 schedule. Taking part is voluntary and needs a manager’s approval.
- Sandia National Laboratories, which offers it to eligible employees with every other Friday off.
The Department of Labor says federal wage law does not address flexible work schedules. It calls such arrangements a matter of agreement between the employer and the employee.
Your own hours
What does a 9-hour day leave you?
A 9-hour workday with an hour for lunch keeps you at work for 10 hours. Take those and 8 hours of sleep out of the 24 in a day, and 6 hours are left for the commute, meals, family and everything else. On a usual 8-hour day the same sum leaves 7.
So on eight days out of every fourteen you have one hour less for yourself, and on one day you have the whole day. To see whether that suits you, count. For two weeks, write down when work really started and stopped, and what you did with the day off. Doing that every day is called time journaling.
What counts as full time in the first place is on how many hours is full time.
A schedule on paper says nine hours. Whether the day really ended there, and what you did with the free Friday, is hard to remember two weeks later.
A good way to keep that count reads your hours from what you already write or say about your day, long days and days off alike, with no timer to start. Most journaling apps record how a long day felt. They do not add up its hours, so you cannot compare one two-week stretch with the next.
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: work, the commute, sleep, time with people, your phone, and the time you never mentioned (shown as unaccounted). Then it shows those hours over days and weeks. So you can see, week by week, how long your long days really were and where your days off went.
1. You write your day
2. It counts the hours
- Work0m
- Sleep0m
- Unaccounted24h
3. It shows your week
Work this week: 0m
On 4 of 7 days. The gaps are the days without it.
An example day and week.
For iPhone and Android. Try it on your own day before you pay.
Sources
Where the rules on this page come from.
Each rule on this page was read on the page of the employer or agency that wrote it.
- U.S. Office of Personnel Management, Pay and Leave handbooks (read ). Alternative Work Schedules.
- California Department of Human Resources, Human Resources Manual (read ). 1503, Alternate Work Week Schedule Policy for Work Week Group 2.
- Sandia National Laboratories, Human Resources (read ). Flexible Work Options.
- U.S. Department of Labor, Wage and Hour Division (read ). Overtime Pay.
- U.S. Department of Labor (read ). Flexible Schedules.
Keep reading.
- Time journalingThe method: write or say your day in your own words, then see it as hours.
- How many hours is part time?Who draws the part-time line in the United States and where, the week as a month and a year, and a calculator for your own shifts.
- How many hours is full time?The official US definitions side by side, the math for a month and a year, and a calculator for your own week.
- Working hours in a yearA full-time year in hours, after holidays and vacation, and what the survey shows.
- Where did my week go? calculatorEnter a typical day and see your week accounted and unaccounted.
Questions
Questions people ask.
How many hours a day do you work on a 9/80 schedule?
You work 9 hours on eight of the days and 8 hours on one. With an hour for lunch, a 9-hour day keeps you at work for 10 hours, for example from 8 AM to 6 PM.
How many days off do you get on a 9/80 schedule?
You get one extra day off every two weeks, which is 26 in a year: 52 weeks ÷ 2. Weekends and holidays come on top of that.
Is a 9/80 schedule the same as a 4/10 schedule?
The two schedules are different. A 4/10 schedule is four 10-hour days every week, with an extra day off each week. A 9/80 schedule has 9-hour days and an extra day off every second week. Both come to 80 hours in two weeks.
When does the workweek start on a 9/80 schedule?
Some employers start it in the middle of the 8-hour day. The State of California does this for its own staff, so each of its work weeks holds 40 hours. Your own employer’s policy says where your workweek starts.
How do I keep track of my hours on a 9/80 schedule?
A notebook is enough: each day, write down when work started and when it stopped, and add up the two weeks. It is easier if the hours are added up for you, so you can compare one two-week stretch with 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 work hours from what you write or say about your day, long days and days off alike, 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.