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Activity Duration and Crew Size Calculator

Turn a quantity of work and a crew's output per day into a duration in working days — or, from a deadline, into the number of crews it takes.

  • Answers as you type
  • Every formula cited
  • Calculated in your browser
SettingsSettings for this calculationUS
Market
Imperial · sales tax
The same arithmetic, solved for the duration or for the crews.

A programme is built one way — the quantity and the crew set the duration — and recovered the other way when the date is fixed first and the question is how many crews it will take to meet it.

How much of the work there is, in the same unit the output rate is measured in.

Any unit will do — an area, a length, a volume or a count of pieces — as long as the output rate below is in the same one. The quantity usually comes straight from a quantity calculator on this site.

What one crew completes in a normal working day, in the quantity's unit.

Your own figure — from past jobs, from the crew leader, or from a pricing book you trust. This page contains no productivity rates: they vary by trade, crew, access, weather and the size of the job far too much for a national average to be honest.

How many crews work on the activity at the same time.

Crews only divide the time if there is room for them to work without waiting for each other. Two crews in one small room do not finish in half the time.

Used to turn working days into weeks.

Only the conversion to weeks uses it; the duration in working days does not change with it.

Duration of the activity

7.5 days

Medium confidence

The work is 15.0 crew-days; 2 crews take 7.5 working days, which a programme shows as 8. The figure is only as good as the output rate entered.

Crew-days of work
15 crew-days
Whole working days to allow
8 days
Weeks at 5 working days a week
1.5 weeks
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • Duration from quantity and production rate, the basis of every activity estimate in a construction programme: crew-days = quantity ÷ output of one crew per working day, and working days = crew-days ÷ crews working at once
  • Crew size for a fixed duration, the same relation solved the other way: crews = crew-days ÷ working days available, rounded up to whole crews

Inputs used

What to Work Out
How long it takes, from the crews
Quantity of Work
600
Output of One Crew per Working Day
40
Crews Working at Once
2
Working Days Available
5
Working Days per Week
5 — Monday to Friday

Intermediate steps

Crew-days of work
15 crew-days
Whole working days to allow
8 days
Weeks at 5 working days a week
1.5 weeks
Final result7.5 days

Confidence note: The work is 15.0 crew-days; 2 crews take 7.5 working days, which a programme shows as 8. The figure is only as good as the output rate entered.

What this calculation does not cover

  • It is only as good as the output rate, which is yours. Output falls on small quantities, awkward access, bad weather and the first days of a new crew on a new task, and none of that is in the arithmetic.
  • Crews divide the time only where there is room for them to work without waiting for each other or for the trade before them.
  • Working days are counted as full days. A calendar with weekends, holidays and a start date is the working-days calculator's job.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-22 · v1.0.0

Regulatory standards & verification citations2
  1. Duration from quantity and production rate, the basis of every activity estimate in a construction programme: crew-days = quantity ÷ output of one crew per working day, and working days = crew-days ÷ crews working at once
  2. Crew size for a fixed duration, the same relation solved the other way: crews = crew-days ÷ working days available, rounded up to whole crews
Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Now that you have the number

These guides cover the work this quantity is for.

How to calculate activity duration and crew size in 7 steps

  1. What to Work OutThe same arithmetic, solved for the duration or for the crews.
  2. Quantity of WorkHow much of the work there is, in the same unit the output rate is measured in.
  3. Output of One Crew per Working DayWhat one crew completes in a normal working day, in the quantity's unit.
  4. Crews Working at OnceHow many crews work on the activity at the same time.
  5. Working Days AvailableThe working days the programme allows for the activity.
  6. Working Days per WeekUsed to turn working days into weeks.
  7. Duration of the activityThe tool computes the duration of the activity from those figures and shows the formula, its sources, and a confidence rating alongside it.

Duration of the activity by quantity of work

Page defaults, not your figures above.

Quantity of WorkDuration of the activity (days)
1001.25
2002.5
5006.25
1,00012.5
2,00025
5,00062.5

Frequently asked questions

Where does the output rate come from?
From you. Your own records of what a crew completed on similar work are the best source, then the crew leader's estimate, then a pricing book you trust — and whichever you use, the same crew on a small, awkward job produces less than on a large, open one. This page carries no rates because an honest national figure does not exist: the output of a bricklaying gang or a drylining crew varies by a factor of two or more with the work, the access and the weather.
Why does doubling the crews not halve the time?
Because they need room and a supply of work. Two crews in one small room get in each other's way, and a crew that finishes its area waits for the trade before it. The arithmetic here assumes each crew works a full day at its normal output, which holds on open, repetitive work and fails in tight spaces.
What is a crew-day?
One crew working one day. It is the unit a quantity turns into before the number of crews is known: 15 crew-days of work is 15 days for one crew, 5 days for three, and roughly 4 days for four once the result is rounded to whole days.
How do I turn working days into a finish date?
With a calendar, because weekends and holidays sit between them. The working-days calculator on this site counts from a start day through the working pattern you choose, and the critical path calculator puts activities in their order once each has a duration.
Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.