Construction & Materials
Rational Method Runoff Calculator (Q=CIA)
Estimate peak stormwater runoff from a drainage area using the rational method, Q = CIA.
Your inputs
Change any value to update the result instantly.
Peak runoff Q
12 ft³/s
Runoff coefficient
0.6
Rainfall intensity
2 in/hr
Drainage area
10 acres
Formula and working
Q = C × I × A
- 1
Collect the inputs
Runoff coefficient C = 0.6; Rainfall intensity I = 2 in/hr; Drainage area A = 10 acres
- 2
Apply the formula
Q = C × I × A
- 3
Result
Peak runoff Q = 12 ft³/s
Frequently asked questions
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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