Construction schedule delay calculator

How to read the result

This calculator treats your activities as a simple chain— each one starts the day after the one before it finishes. Add a delay to any activity and everything after it shifts forward by the same number of days. That’s the cascade effect: one late trade doesn’t just cost you the delay itself, it costs every downstream trade the same number of days, all the way to your finish date.

Real projects usually have some slack between trades—time built in before the next crew genuinely needs the site. A delay that fits inside that slack doesn’t move your finish date at all. This tool doesn’t model slack; it’s meant to show the worst case so you can see how much a “small” delay actually compounds when trades are stacked back-to-back.

Frequently asked questions

How do I calculate a construction schedule delay?

Add the delay in days to the delayed activity’s duration, then shift every downstream activity that depends on it forward by the same number of days. If nothing downstream depends on the delayed activity, your finish date doesn’t move at all.

Does every delay push back my finish date?

No. Only delays on your critical path—the longest chain of dependent activities—move your finish date. An activity with slack can slip a few days without affecting your schedule at all.

What’s the difference between this and a real cascade engine?

This tool assumes zero lag and no slack between activities, which is rarely how a real project runs. A real cascade engine tracks actual dependency links and slack per activity, so it tells you precisely which delays matter and recalculates every affected date automatically the moment one changes.