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How to Calculate Man-Hours for a Job

By Frame Sixty Labs · Last updated: October 5, 2026

What is a man-hour?

A man-hour is one hour of work done by one person. It measures the amount of labor in a job, independent of how many people shared it: one person working 8 hours and four people working 2 hours each are both 8 man-hours.

Person-hours, labor hours and work hours mean exactly the same thing, and many estimates and contracts now use those terms instead. The arithmetic does not change with the name.

Man-hours are what you use to price a job, bill labor, compare an estimate with what really happened, and work out how long the next job will take.

What is the man-hours formula?

When everyone works the same hours, it is one multiplication:

man-hours = number of workers × hours each worked

Over several days, multiply by the days as well: 4 people × 8 hours × 3 days = 96 man-hours.

That formula is fine for a plan. It is rarely right for a finished job, because real crews do not work identical hours. Someone starts late, someone leaves for another site, one day runs long. For actual man-hours the formula becomes a sum:

man-hours = person 1’s hours + person 2’s hours + …

How do you calculate man-hours step by step?

1. List everyone who worked on the job. One row per person, one column per day. Count only time spent on this job.
2. Work out each person’s hours for each day. Finish time minus start time, minus any unpaid break. 7:00 AM to 4:00 PM is 9:00; less a 0:30 lunch it is 8:30. If the subtraction is the hard part, see how to calculate hours between two times.
3. Add each person’s days in hours and minutes. Add the minutes and carry every 60 into an hour.
4. Add the people together. That sum is the man-hours for the job.
5. Cross-check by day. Add the crew’s hours for each day, then total the days. Both routes must land on the same number.
6. Convert to decimal hours once, at the end. Keep the hours and divide the minutes by 60.
7. For cost, multiply each person’s hours by their own rate and add the results.

Worked example: a four-person crew on a three-day job

A crew of four builds a deck over three days. These are each person’s hours on the job, after unpaid lunch breaks:

By person: the lead is 8:30 + 9:10 = 17:40, + 7:20 = 25:00. Carpenter A is 8:30 + 8:45 = 17:15, + 7:20 = 24:35. Carpenter B is 8:00 + 8:45 = 16:45, + 4:30 = 21:15. The helper is 6:15 + 8:45 = 15:00, + 7:20 = 22:20.

Add the people: 25:00 + 24:35 = 49:35, + 21:15 = 70:50, + 22:20 = 93:10.

Cross-check by day: 31:15 + 35:25 = 66:40, + 26:30 = 93:10. The two routes agree, so the total is right.

Convert: 93:10 is 93 + 10 ÷ 60 = 93.17 man-hours. Need a refresher on carrying minutes? See how to add hours and minutes.

Why isn’t it just crew size times 8 hours?

Because the shortcut counts hours nobody worked and misses hours somebody did. Four people for three 8-hour days is 4 × 3 × 8 = 96 man-hours. The timesheets say 93:10. The shortcut is 2:50 too high.

In this example the helper arrived late on day one, Carpenter B left early on day three, and day two ran long for everyone. None of that shows up in “4 people, 3 days.” If you bill labor by the hour, 96 overbills the client; if you use it to judge the estimate, it hides that the job came in under.

Two related mistakes are worth naming:

• Using the job’s clock span. A site open from 7:00 AM to 4:00 PM is a 9-hour span. With a 30-minute unpaid lunch that is 8:30 of work per person at most, and less for anyone who was not there the whole time.
• Treating H:MM as a decimal. 93:10 is 93.17, not 93.10. Minutes are sixtieths of an hour, not hundredths. Hours to decimal covers every conversion.

How do you turn man-hours into labor cost?

Multiply each person’s decimal hours by that person’s hourly rate, then add. Say the lead costs $38.00 an hour, each carpenter $30.00, and the helper $22.00:

Dividing the cost by the hours gives the job’s blended rate: $2,816.33 ÷ 93.1667 = $30.23 per man-hour.

Notice that this is not the plain average of the four rates. ($38 + $30 + $30 + $22) ÷ 4 = $30.00, and 93.1667 × $30.00 = $2,795.00, which is $21.33 short. The simple average only works when everyone puts in the same hours. Here the highest-paid person worked the most, so the real blend is higher.

These figures are wages only. A full labor cost adds whatever you carry on top of wages, such as payroll taxes, insurance and benefits, and any overtime premium. Overtime does not change the man-hours, only what some of them cost; see how to calculate overtime and how to calculate pay from hours worked.

How do you estimate how long a job will take from man-hours?

Turn the formula around. Divide the job’s man-hours by the man-hours your crew produces in a day:

working days = man-hours ÷ (crew size × hours per day)

For a job estimated at 120 man-hours on 8-hour days:

The same equation gives crew size if the deadline is fixed: to finish 120 man-hours in 3 days of 8 hours you need 120 ÷ (3 × 8) = 5 people.

Treat the result as arithmetic, not a promise. Doubling a crew rarely halves the calendar: people get in each other’s way, some tasks cannot be split, and some have to wait for others to finish or cure. The estimate is a starting point that your own finished jobs should correct.

Using a finished job to estimate the next one

Divide the man-hours by the amount of work to get your own rate. If the deck above was 320 square feet, the crew spent 93.1667 ÷ 320 = 0.291 man-hours per square foot, about 17.5 minutes each.

A similar 450-square-foot deck would then be roughly 450 × 0.291 = 131 man-hours. With four people on 8-hour days that is 131 ÷ 32 = 4.1, a little over four working days. This is a rate from one job by one crew, not an industry standard; it gets more reliable as you record more jobs.

What are man-days and full-time equivalents?

They are man-hours in bigger units, using the usual full-time conventions:

• Man-day: 8 man-hours. The example job is 93.17 ÷ 8 = 11.65 man-days.
• Man-week: 40 man-hours.
• Full-time year (one FTE): 40 × 52 = 2,080 man-hours. How many work hours are in a month shows where that figure comes from.

Check which convention a contract or bid uses before converting. A crew on 10-hour days has 10-hour man-days, and the numbers will not match an 8-hour assumption.

What are the most common man-hour mistakes?

• Multiplying headcount by a standard day. It gave 96 instead of 93:10 above. Use the hours people actually logged.
• Leaving unpaid breaks in. Twelve worker-days with a 0:30 lunch each is 6:00. Count from arrival to departure and the example reads 99:10. See paid vs unpaid breaks on a timesheet.
• Typing minutes as decimals. 24:35 is 24.58 hours, not 24.35.
• Converting every entry to decimal, then adding. Rounded figures drift. Add in hours and minutes and convert the total once.
• Pricing the total at an average rate. It was $21.33 off on a small job. Price each person at their own rate.
• Mixing jobs. If someone splits a day between two sites, split their hours too, or one job looks expensive and the other looks cheap.

Frequently asked questions

What is the formula for man-hours?

Number of workers × hours each one worked, when everyone works the same hours: 4 × 8 = 32 man-hours. When hours differ, man-hours are the sum of each person’s hours.

Are man-hours, person-hours and labor hours the same thing?

Yes. They all mean one hour of work by one person. Person-hours and labor hours are the gender-neutral terms, and many estimates and contracts now use them.

How many man-hours are in a day, a week and a year?

For one full-time person on the usual convention: 8 in a day, 40 in a week, and 2,080 in a year (40 × 52). Multiply by the number of people for a crew: five people for one 8-hour day is 40 man-hours.

Do breaks and travel time count as man-hours?

Unpaid meal breaks are normally left out, because nobody was working and nobody is paid for them. Whether travel, setup and cleanup count depends on what the figure is for and on your pay rules. Decide once, and count it the same way on every job so your numbers stay comparable.

How do I convert man-hours to days?

Divide by the man-hours the crew works per day. A 120 man-hour job with 3 people on 8-hour days is 120 ÷ 24 = 5 working days. Dividing by 8 alone gives man-days: 120 man-hours is 15 man-days.