Storm Drain Calculator
Static · formula-only · worked example computed when this page was built · no live data
The Storm Drain Calculator uses the Rational Method to find the design stormwater flow for a catchment. Example: for a 1 ha catchment (C = 0.7) at 150 mm/h, 10-year return, Design flow = 291.7 L/s, Runoff coefficient = 0.7, Time of concentration = 6.8 min (per DPWH Blue Book | Rational Method).
How it works
Computed from your inputs per DPWH Blue Book | Rational Method. Anything the worked example does not state uses this calculator's standard default; the interactive version shows every input and lets you change it.
Worked example (Plumbing & Pumps)
Inputs: a 1 ha catchment (C = 0.7) at 150 mm/h, 10-year return.
| Result | Value |
|---|---|
| Design flow | 291.7 L/s |
| Runoff coefficient | 0.7 |
| Time of concentration | 6.8 min |
Computed by WorkHive's calculation engine when this page was built; standard: DPWH Blue Book | Rational Method.
How to use this calculator
- Read the worked example. It uses a 1 ha catchment (C = 0.7) at 150 mm/h, 10-year return and shows every number in the method.
- Follow the formula with your own figures: it returns Design flow, Runoff coefficient, Time of concentration, computed per DPWH Blue Book | Rational Method.
- To compute interactively, open the Storm Drain Calculator inside WorkHive's free Engineering Design suite (link below). It runs the same method with your inputs.
FAQ
What is a storm drain rational method calculator?
The Storm Drain Calculator is a free online tool that uses the Rational Method to find the design stormwater flow for a catchment. It shows the formula and a fully worked example so you can check the method, not just the number.
How is it calculated?
The result is computed from your inputs following DPWH Blue Book | Rational Method. The worked example on this page shows a real computation with real numbers.
Is the calculator free?
Yes. WorkHive is free: this worked example is open to everyone, and the interactive calculator runs inside the free Engineering Design suite after a free sign-up (your work is saved to your account). WorkHive is a free, offline-first maintenance platform built for Philippine industrial plants.
Run it on your own numbers
Open the interactive Storm Drain Calculator in WorkHive. Free, and a free sign-up saves your calculations, BOMs and scope-of-works to your account.