Perform common stormwater calculations quickly using Rational Method, Tc, and Detention Volume tools.
Users
12
−1 in 30 days
Rating
0.0 / 5
unchanged in 30 days
Ratings
0
0 in 30 days
Store rank
#189K
#158K among extensions
Version
1.0.3
updated 19 Jan 2026
Users
monthly, 16 months
Latest, 21 Oct 2026:12 usersMove the mouse over the chart for any month
Ratings count
monthly, 16 months
Latest, 21 Oct 2026:0 ratingsMove the mouse over the chart for any month
The Chrome Web Store rounds user counts down to the leading digit, so the user line moves in steps. The ratings count is exact and is the better signal of real adoption.
About StormCalc – Essential Stormwater Tools
StormCalc is your all-in-one toolkit for stormwater and dam volume calculations. Designed for civil and hydraulic engineers, consultants, and field practitioners, this tool streamlines common hydrological calculations into a single, easy-to-use Chrome extension
Features:
Rational Method:
-Quickly estimate peak flow (Q) using runoff coefficient, intensity, and area.
Time of Concentration (Tc):
-Calculates Tc using the Bransby-Williams method with flexible unit inputs.
Detention Volume Calculator:
-Compares pre- and post-development scenarios with auto-generated hydrograph and required detention storage.
Manning’s Equation (NEW):
-Computes flow rate for both circular and rectangular pipes with built-in roughness coefficients.
Dam Volume Estimators:
-Quick Method
-Square Dam
-Circular Dam
-Gully Dam