Sådan bruger du Gutter Capacity Calculator — estimate gutter capacity for a roof
Estimate design rainwater flow from effective roof catchment area, rainfall intensity and a transparent safety allowance.
Flow in litres per second = area in m² × rainfall in mm/hour ÷ 3,600, with the selected safety allowance applied.
Estimate design rainwater flow from effective roof catchment area, rainfall intensity and a transparent safety allowance. The linked Sellible tool keeps the fields, units and output together so the assumptions can be reviewed before the result is used.
- 1
Determine effective rather than plan roof area where required.
- 2
Use an appropriate local design rainfall intensity.
- 3
Compare calculated flow with a complete gutter and outlet system.
Example values and result
These values demonstrate the method; replace them with measurements, rates or file details that match the real task.
- Effective roof area
- 80 m²
- Design rainfall
- 75 mm/hour
- Base flow
- 1.67 L/s
- Safety allowance
- 20%
The example produces a planning flow near 2.0 L/s. Final gutter, outlet and downpipe selection must follow local standards and manufacturer capacity data.
Nøjagtighed og praktisk vejledning
- Consider valley discharge and concentrated flows.
- Check gutter fall, outlet position and downpipe capacity together.
- Allow for blockage, maintenance and overflow risk.
Common mistakes
- Sizing only the gutter while ignoring outlets and downpipes.
- Using annual rainfall instead of design intensity.
- Assuming a safety factor replaces local drainage design.
A free account makes repeat tasks simpler
Email-link sign-in keeps file jobs, downloads, support and usage available across devices. Browser calculators remain free.
Ofte stillede spørgsmål
Is Gutter Capacity Calculator free?
Yes. This calculator or browser utility is free and does not use processing credits.
Can I use this guide and Gutter Capacity Calculator on a phone?
Yes. The guide, inputs, results and calls to action are responsive and keyboard accessible on current phones, tablets and desktop browsers.
Should I order or make a decision from the estimate alone?
No. Consider valley discharge and concentrated flows. Check gutter fall, outlet position and downpipe capacity together. The calculation is a planning aid rather than professional or regulatory approval.
How should I check the result?
Keep the source values and units visible, compare the result with supplier or project information, and retain enough precision until the final purchasing or reporting step.