Gutters and downspouts
Gutter-to-barrel yield calculator
Estimate rainwater collection from gutter. Rain barrel planning.
Try the calculation
Use the catchment formula for a rainfall event.
Adjustable example. Change these illustrative inputs to match your task, then recalculate. Reset restores the example and its result.
Understand the result
How this calculation works
Gutter-to-barrel yield estimates potential event volume from a catchment.
Steps
- Enter plan catchment area, rainfall depth and runoff coefficient.
- Use a coefficient that reflects the surface assumption.
The form starts with the worked example below. Change its values and selections to match your task; Reset restores the example.
Formula
gallons = area × rainfall depth × coefficient × 0.623.
Variables and units
- Catchment area (sq ft)
- Required. Use a positive value. Starting example: 1000. Replace it for your task.
- Rainfall depth (in)
- Required. Zero is accepted. Starting example: 1. Replace it for your task.
- Runoff coefficient (ratio)
- Required. Zero is accepted. Starting example: 0.8. Replace it for your task.
What the result means
It does not model first-flush diversion, barrel capacity, overflow or storage timing.
Worked example
Inputs: Catchment area = 1000; Rainfall depth = 1; Runoff coefficient = 0.8.
Calculation: 1,000 sq ft × 1 in × 0.8 × 0.623 = 498.4 gallons.
Result: 498.4 gallons.
Frequently asked questions
Is this the water stored?
No, it is potential volume reaching the modeled collection path.
Can the coefficient be zero?
Yes.
Does gutter length affect the result?
Not in this catchment-area model.