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Roof Drainage Capacity Calculator
Estimate rainwater flow from a roof for sizing drainage.
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Estimate rainwater flow from a roof for sizing drainage.
Roof Drainage Capacity Estimator
Enter your numbers below for an instant estimate.
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💡 Tip: Use local design rainfall intensity.
How It Works
Key concepts behind this calculator
1
Enter Values
Fill in each field with your own numbers.
2
Calculate
Results update as you change the inputs.
3
Review
Read the breakdown and the explanation.
4
Adjust
Change values to compare scenarios.
Quick Reference Guide
Roof Quick Guide
Typical values for reference.
| Area | Rainfall | Coeff | Flow L/s |
|---|---|---|---|
| 60 | 75 | 0.95 | 1.19 |
| 120 | 75 | 0.95 | 2.38 |
| 120 | 100 | 0.95 | 3.17 |
| 200 | 50 | 0.95 | 2.64 |
| Rule of Thumb | Check inputs | Use as a guide | Round sensibly |
Common Questions
Roof Drainage Capacity Calculator FAQ
Answers to common questions about this calculator.
Use local design storm data.
It gives a quick estimate of roof drainage capacity from the values you enter.
No. It is a planning estimate, so check important figures with a professional or official source.
Yes. Edit any field and the result updates when you calculate.