Calculation sequence
Step-by-step method
- Confirm the calculation boundary, units, and source of every input.
- Apply the displayed equation to the entered values.
- Review the result against governing criteria and documented uncertainty.
PlumbingBeginnerStormwater
Rainfall-Depth Runoff-Volume Calculator
Convert tributary area, storm depth, and runoff factor into a runoff volume.
Why it matters: A transparent formula keeps the user-entered hydraulic, gas, or storage basis available for technical review.
Calculated result
Engineering evaluation
Rainfall runoff volume (V_r)11,844.16 gal
Engineering interpretation
The entered area and rainfall depth produce 11844.16 gal of runoff volume.
Important limitations
- Uniform-depth volume only. Temporal distribution, infiltration, depression storage, initial abstraction, routing, detention, and jurisdictional hydrology methods are separate.
Engineering knowledge center
Understand the calculation—not just the answer
Governing relationships
V_r=A·d·C with consistent area, depth, and volume conversions
Current substitution
V_r=10000×2×0.95 with the displayed unit conversion=11844.16 gal.
Equation legend
Inputs and calculated quantities
- A
- Tributary area — ft² or m²
- d
- Storm rainfall depth — in or mm
- C
- Runoff factor — 0–1
- V_r
- Rainfall runoff volume — gal
Applications
How this calculation is used
Building design
Screen a documented system relationship without embedding a protected design table.
Construction
Check submittal and field values using the same visible inputs.
Commissioning
Reconcile measured and scheduled conditions before professional disposition.
Quality controls
Assumptions and limitations
Assumptions
- Inputs describe one documented system boundary and compatible operating condition.
- All values use the displayed symbols and one consistent unit system.
Limitations
- This screen does not establish code compliance, final design, equipment selection, or acceptance.
- Adopted codes, local criteria, manufacturer data, uncertainty, and professional judgment remain controlling.
Field use
Verification procedure
- Identify the calculation boundary and source of each input.
- Record representative values with compatible pressure, temperature, flow, and time bases.
- Review the result against the adopted criteria, manufacturer data, and uncertainty.
Common engineering mistakes
- Mixing standard and actual gas volumes or gauge and absolute pressures.
- Treating an arithmetic screen as a code-sizing table or hidden acceptance criterion.
Technical basis
References and source standards
- NOAA Precipitation-Frequency DataLocation-, duration-, and recurrence-specific rainfall data must be selected by the user.
- International Plumbing CodeAdopted edition and local amendments govern; protected sizing tables are not reproduced.
- NIST SI and Unit GuidanceUnit and dimensional-conversion basis.
Engineering calculation disclaimer
These engineering tools are provided for educational, preliminary evaluation, field verification, and commissioning support. Results depend on the accuracy of user-entered information and the assumptions stated for each calculation. Every colored status and comparison is a screening indicator only; project criteria, contract requirements, applicable codes, manufacturer instructions, measurement uncertainty, and authorized engineering judgment govern. The tools do not replace project-specific engineering analysis or the judgment of a licensed professional engineer.
Read the full use and limitation statement