Construction Working Days Calculator
Site work days excluding weekends, holidays and weather/rain days.
Written and maintained by Paul Clark, Redmoon Software · Rules last verified
These calculators are for informational purposes only and do not constitute legal, financial, or professional advice.
How the Construction Working Days Calculator works
The Construction Working Days Calculator counts the days a crew can actually be on site between two dates, and then removes the days lost to weather. That second step is what separates a construction count from a plain business-day count: a framing day lost to rain is not a weekend and not a public holiday, but it is still a day nobody worked, and it still moves the finish date.
The tool takes the calendar span, removes weekends according to your work-week pattern — six-day site weeks are common and are supported — removes the public holidays for the country you select, and removes any custom dates you add for site-specific closures. It then subtracts the number of weather or stand-down days you enter, and reports both figures separately: the working days that were available, and the productive days left after weather. Keeping them apart is the point, because a delay claim has to show what was lost and to what cause, not just a net total.
Enter weather days as a count rather than as specific dates because that is how site records usually hold them — a tally from the daily diary or the site log. If you do know the exact dates and want them itemised in the day-by-day breakdown, add them as custom closures instead and leave the weather count at zero; the arithmetic is identical and the breakdown then shows precisely which days dropped out. What the calculator cannot do is decide whether a given day was genuinely unworkable: wet-weather entitlement is defined by your contract, usually by reference to rainfall thresholds or to a superintendent’s determination, and that judgment stays with you.
Worked example
A pour sequence runs from Monday, 1 June 2026 to Tuesday, 30 June 2026 under a US calendar and a Monday-to-Friday site week. The span holds 30 calendar days, of which 8 are weekend days and one — Juneteenth, on Friday 19 June — is a federal holiday, leaving 21 working days available. The site diary records four wet-weather stand-downs. The calculator returns 17 productive site days, and shows the 21 and the 4 as separate lines — which is the form a progress claim or an extension-of-time submission needs, because it evidences the loss rather than just asserting the net.
Frequently asked questions
Why enter weather days as a count instead of dates?
Because that is how site records usually hold them — a running tally from the daily diary rather than a tidy list. The count keeps data entry to one field for a claim covering several months. If you do have the exact dates and want them itemised, add them to the custom holidays field instead and leave the weather count at zero; the result is the same and the day-by-day breakdown then marks each one.
Does it handle a six-day site week?
Yes. Set the work-week pattern to include Saturday and the count treats Saturdays as available working days, which materially changes the figure over a long programme. Public holidays and custom closures still drop out on top of that. Match the pattern to the one in the contract programme rather than to a standard office week, or the available-days figure will understate what the programme assumed.
Can this substitute for an extension-of-time claim?
No. It gives you the day arithmetic, cleanly separated by cause, which is the evidentiary spine of a claim. Entitlement itself depends on the contract: which weather events qualify, what rainfall or ground-condition thresholds apply, what notice you must give and within what period, and whether the delay is on the critical path at all. Take the numbers from here and the entitlement question to the contract and your delay consultant.
What this calculator does not do
A limitation you know about costs far less than one you find after the deadline. These are the specific things this tool cannot work out for you.
- Weather days are a number you enter, not a forecast. Most construction contracts define what qualifies as an inclement-weather day and require notice before it can be claimed.
- It does not model programme float, acceleration or concurrent delay, which are what an extension-of-time claim actually turns on.
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