The phrase survives from a time when it named a fixed arrangement. It now names a schedule whose paid length moves by a full hour depending on how lunch is treated, and that gap between the clock and the timesheet is why the question keeps getting asked.
How many hours is 9 to 5? Eight hours elapsed, but the paid figure depends on the meal period. With an unpaid hour for lunch it is 7 hours a day, or 35 a week. With an unpaid half hour it is 7.5, or 37.5 a week. Only a 9 to 5 with no unpaid break reaches 8 and 40.
So the same schedule produces a 35-hour week or a 40-hour week depending on one line in a contract, and 5 hours a week is not a rounding difference.
What does the arithmetic actually give?
Nine in the morning to five in the evening is 8 hours of elapsed time, because 17:00 minus 09:00 is 8. Everything after that is subtraction, and every row below is the same subtraction run at different inputs. The weekly column is the daily figure times 5, and the annual column is the weekly figure times 47, which is a year after roughly three weeks of vacation and two weeks of public holidays.
| Start | End | Elapsed | Unpaid break | Paid hours | Per week | Per year (47 weeks) |
|---|---|---|---|---|---|---|
| 9:00 | 17:00 | 8:00 | none | 8.00 | 40 | 1,880 |
| 9:00 | 17:00 | 8:00 | 0:30 | 7.50 | 37.5 | 1,762.5 |
| 9:00 | 17:00 | 8:00 | 1:00 | 7.00 | 35 | 1,645 |
| 9:00 | 17:30 | 8:30 | 0:30 | 8.00 | 40 | 1,880 |
| 8:30 | 17:00 | 8:30 | 1:00 | 7.50 | 37.5 | 1,762.5 |
| 9:00 | 18:00 | 9:00 | 1:00 | 8.00 | 40 | 1,880 |
| 8:00 | 17:00 | 9:00 | 0:45 | 8.25 | 41.25 | 1,938.75 |
Take the third row as the worked example. Eight hours elapsed less a one-hour unpaid lunch is 7 hours paid. Five days is 7 x 5 = 35 hours a week. Across 47 working weeks that is 35 x 47 = 1,645 hours a year.
Now compare it with the first row: 40 x 47 = 1,880. The difference is 1,880 minus 1,645, which is 235 hours a year, or about six standard weeks of work, produced entirely by whether lunch is paid. That is the number worth carrying away from this page.
One more thing falls out of the table. A 9 to 5 with an hour for lunch is a 35-hour week, and 35 is exactly where the Bureau of Labor Statistics draws the line between full time and part time in its statistics. The archetypal full-time schedule sits on the boundary rather than comfortably inside it. How many hours is full time sets out the three different thresholds in play.
Why is lunch not counted?
Because in the United States a genuine meal break is not working time, and the regulation says so in plain language. 29 CFR 785.19 states that “bona fide meal periods are not worktime”, that they “do not include coffee breaks or time for snacks”, and that “the employee must be completely relieved from duty for the purposes of eating regular meals”. It sets a rough length: “ordinarily 30 minutes or more is long enough for a bona fide meal period”, with shorter periods possible under special conditions.
The relieved-from-duty test is the operative part, and the regulation gives its own examples: “an office employee who is required to eat at his desk or a factory worker who is required to be at his machine is working while eating”. The section adds that an employee does not have to be allowed to leave the premises, as long as they are otherwise completely freed from duties.
Short breaks are treated the opposite way. 29 CFR 785.18 says rest periods “running from 5 minutes to about 20 minutes” are common in industry, that they “promote the efficiency of the employee and are customarily paid for as working time”, and that they “must be counted as hours worked”. So under those US federal rules a coffee break inside a 9 to 5 does not come out of the total, and an eating break where you are genuinely off duty does. Both sections sit under the Fair Labor Standards Act and describe what counts as hours worked in the United States rather than what breaks anyone is entitled to.
Does anyone have to give you a lunch break?
Under US federal law, no. The FLSA regulations quoted above say what happens to a break when one is given; they do not require one. Some US states do mandate meal periods, so the answer where you live is a state question rather than a federal one, and it is worth reading your own state’s rule rather than a national summary.
The United Kingdom does legislate a break, and it is smaller than most people expect. GOV.UK states that workers have the right to “one uninterrupted 20 minute rest break during their working day, if they work more than 6 hours a day”, and that “the break does not have to be paid, it depends on their employment contract”. The same UK guidance sets 11 hours of rest between working days, and either 24 uninterrupted hours off each week or 48 each fortnight.
So the British version of a 9 to 5 has a statutory 20-minute floor whose paid status is contractual, which produces yet another daily figure: 8 hours elapsed less 20 minutes is 7 hours 40 minutes, and 40 divided by 60 is 0.667, so 7.67 hours. Five days of that is 38.33 a week, and 38.33 x 47 is about 1,802 hours a year. Different jurisdiction, different arithmetic, same schedule on the door.
What about the time that is not on either side of the line?
The table above is the contractual picture, and the actual day is usually wider than the contract. Under the US Fair Labor Standards Act, the Department of Labor’s fact sheet on hours worked states that an employee traveling from home before the regular workday and back at the end of it “is engaged in ordinary home to work travel, which is not work time”, and that “work not requested but suffered or permitted to be performed is work time that must be paid for by the employer”. So in the United States the commute is outside the count and the mail you answered at eight in the morning is inside it. Staying to finish something at half past five is time you spent whether or not anyone counts it, and the travel and on-call rules differ by jurisdiction.
This is where the arithmetic stops being a lookup and becomes a measurement. The question “how many hours is my 9 to 5” has a contract answer, which you can read, and a real answer, which nobody has written down. How to calculate work hours covers the method for turning start and finish times into a defensible daily figure, and the hours calculator will run your own times and breaks rather than the seven combinations above.
One unit note. Payroll and billing systems store durations as decimals, not as clock time, so 7 hours 40 minutes is 7.67 and not 7.40. Typing the clock version into a spreadsheet is the most common way a week of correct entries produces a wrong total, and decimal hours sets out the conversion.
Which number should you use?
Use 8 when someone asks how long a 9 to 5 is, because that is the elapsed time and it is what the phrase means. Use your paid figure, 7 or 7.5 or 7.67, whenever the number feeds a rate, a timesheet or an annual total, because that is the one your contract and your jurisdiction actually describe. And use your measured figure, which is neither of those, whenever you are deciding whether the arrangement is working.
That last one is the only figure nobody can hand you. Timeness is for producing it: make an activity for work and a few for the parts of the day you suspect, tap once to start and once to switch, and the day timeline shows where the eight hours went while the week and month charts add them up. Everything stays on the device with private iCloud sync, and there is no account to make.
After four weeks you can put your own daily average into the table above instead of 8. If the elapsed figure comes out larger than your contract and the paid figure smaller, that gap is exactly why the question sounds simple and is not. A time audit is the structured version of that four weeks.