Mathematics · Geometry

Hydraulic Radius Calculator

Calculate hydraulic radius from flow cross-sectional area and wetted perimeter.

Runs locally
Your numbers

Inputs and results stay in this browser. Change one value at a time to explore the relationship.

Your inputCalculatedPassed forward in chains
hydraulic radius1.5

Calculation steps

  1. Use c=a/b with flow cross-sectional area=18 and wetted perimeter=12.
  2. hydraulic radius=1.5.

Understand Hydraulic Radius

One idea, three depths

Choose how deeply to explain Hydraulic Radius

Calculate hydraulic radius from flow cross-sectional area and wetted perimeter.

Age 5Explain it to a 5-year-oldStart with a picture

Imagine using Hydraulic Radius to answer this question: calculate hydraulic radius from flow cross-sectional area and wetted perimeter? Enter flow cross-sectional area and wetted perimeter; the calculator shows hydraulic radius. For example: flow cross-sectional area=18 and wetted perimeter=12 produce hydraulic radius=1.5. The answer tells you hydraulic radius.

Age 15Explain it to a 15-year-oldConnect it to the formula

Hydraulic radius divides flow area by wetted perimeter. This page evaluates the relationship directly. The rule is c=a/b. Its input values are flow cross-sectional area, wetted perimeter, and the main result is hydraulic radius. For example: flow cross-sectional area=18 and wetted perimeter=12 produce hydraulic radius=1.5.

CollegeExplain it at college levelState the model precisely

This calculator evaluates the stated hydraulic radius relation over the valid real-number domain stated below. The implemented relation is c=a/b, evaluated from flow cross-sectional area, wetted perimeter to produce hydraulic radius. Hydraulic radius divides flow area by wetted perimeter. This page evaluates the relationship directly. Wetted perimeter excludes a free surface unless the chosen convention states otherwise.

Inputs and valid domain

  • flow cross-sectional area must be a finite real number.
  • wetted perimeter must be a finite real number.

Important boundary: Wetted perimeter excludes a free surface unless the chosen convention states otherwise.

The formula

c=a/b

How the calculator works through it

It substitutes flow cross-sectional area, wetted perimeter into the formula and exposes every numerical step above. The main output is hydraulic radius.

Read the result correctly

The hydraulic radius is the direct answer to “calculate hydraulic radius from flow cross-sectional area and wetted perimeter.” Read it with the units shown beside the inputs; a sign, angle, percentage or rate changes what the number means.

A worked check

flow cross-sectional area=18 and wetted perimeter=12 produce hydraulic radius=1.5.

Where this model stops being reliable

Wetted perimeter excludes a free surface unless the chosen convention states otherwise.

Learn it by changing one value

Begin with the worked example, then change one value while keeping the others fixed. Compare the new result and calculation steps to identify which part of the formula changed.

Dictionary terms behind this calculator

Before studying the codeWhat you should know firstUse the calculator immediately, or check the foundations before reading the implementation.

These foundations help you understand why Hydraulic Radius works. They never block the calculator, and “optional” means useful context rather than a hidden requirement.

Hard requirements

  • Reading formulas and substituting values

    Hydraulic Radius uses c=a/b. You need to recognise what each side represents before substituting the stated inputs or rearranging the relationship.

    Review this foundation about 4 min

Strong support

Optional enrichment

  • Angles and geometric relationships

    Angle language provides useful geometric context for extending Hydraulic Radius to related shapes and constructions.

    Review this foundation about 4 min
Learn the missing foundationsI already know these — show the code

Mathematics → algorithm → program

Implement this calculation in code

These are direct reference implementations of the calculator's principal relationship and first output. They run locally and include a small known-answer check where the language supports it.

Algorithm

  1. Read flow cross-sectional area, wetted perimeter.
  2. Evaluate the principal relationship: c=a/b.
  3. Return hydraulic radius and check the domain conditions described above.
Python
            from math import *

def hydraulic_radius_calculator(a, b) -> float:
    return (a / b)

assert abs(hydraulic_radius_calculator(18, 12) - 1.5) < 1e-6 * max(1.0, abs(1.5))
          
Current calculator valuesUpdates when you change an input above.
              
            
C
            #include <assert.h>
#include <math.h>

double hydraulic_radius_calculator(double a, double b) {
    return (a / b);
}

int main(void) {
    const double expected = 1.5;
    const double actual = hydraulic_radius_calculator(18, 12);
    assert(fabs(actual - expected) < 1e-6 * fmax(1.0, fabs(expected)));
}
          
Current calculator valuesUpdates when you change an input above.
              
            
C++
            #include <cassert>
#include <cmath>
#include <numbers>

double hydraulic_radius_calculator(double a, double b) {
    return (a / b);
}

int main() {
    constexpr double expected = 1.5;
    const double actual = hydraulic_radius_calculator(18, 12);
    assert(std::fabs(actual - expected) < 1e-6 * std::fmax(1.0, std::fabs(expected)));
}
          
Current calculator valuesUpdates when you change an input above.
              
            
Linux x86-64 assembly

x86-64 NASM · System V ABI · Linux · SSE2 with libm where required

            ; double hydraulic_radius_calculator(double a, double b)
; Linux x86-64 NASM · System V ABI · first eight doubles in xmm0–xmm7
global hydraulic_radius_calculator
section .text

hydraulic_radius_calculator:
    push rbp
    mov rbp, rsp
    sub rsp, 32
    movsd [rbp-8], xmm0
    movsd [rbp-16], xmm1
    movsd xmm0, [rbp-8]
    divsd xmm0, [rbp-16]
    movsd [rbp-24], xmm0
    movsd xmm0, [rbp-24]
    leave
    ret
          
Current calculator valuesUpdates when you change an input above.
              
            
MATLAB
            function result = hydraulic_radius_calculator(a, b)
    result = (a / b);
end
          
Current calculator valuesUpdates when you change an input above.
              
            
Wolfram Language
            ClearAll[mwCalculate];
mwCalculate[a_, b_] := (a / b);
          
Current calculator valuesUpdates when you change an input above.
              
            

Continue in mathematical software

The downloaded file includes your current inputs and first calculated result. It is created locally.

Floating-point answers can differ slightly by language, compiler and processor. Compare within a suitable tolerance rather than assuming every decimal representation will be identical.

Supporting sourcesAcademic referencesPrimary standards, textbooks and complete citations

Standards, reading and academic references

Use the calculator as the worked interaction, then consult the primary standards and academic textbooks listed below. MW SysArc links to the original sources; the explanation on this page is original and does not reproduce them.

Algebra and Trigonometry 2e

Read the related free OpenStax mathematics chapters
Cite this book
APA 7
Abramson, J. (2021). Algebra and trigonometry 2e. OpenStax. https://openstax.org/books/algebra-and-trigonometry-2e/pages/1-introduction-to-prerequisites
MLA 9
Abramson, Jay. Algebra and Trigonometry 2e. OpenStax, 2021, https://openstax.org/books/algebra-and-trigonometry-2e/pages/1-introduction-to-prerequisites.
Chicago author-date
Abramson, Jay. 2021. Algebra and Trigonometry 2e. Houston, TX: OpenStax. https://openstax.org/books/algebra-and-trigonometry-2e/pages/1-introduction-to-prerequisites.

OpenStax entries are free to read online. Follow the licence shown on each linked source before redistributing or adapting its content.

Reuse the page responsiblyCite this pageAPA, MLA, Chicago, Harvard, BibTeX and RIS

These formats cite this calculator page itself. They are separate from the academic references above, which support the mathematical method and terminology.

APA 7

MW SysArc. (2026, July 21). Hydraulic Radius Calculator. MW SysArc Tools. https://math.mwsysarc.com/geometry/hydraulic-radius-calculator

MLA 9

MW SysArc. “Hydraulic Radius Calculator.” MW SysArc Tools, 21 July 2026, https://math.mwsysarc.com/geometry/hydraulic-radius-calculator. Accessed 31 Aug. 2026.

Chicago 17

MW SysArc. “Hydraulic Radius Calculator.” MW SysArc Tools. Published July 21, 2026. Accessed August 31, 2026. https://math.mwsysarc.com/geometry/hydraulic-radius-calculator.

Harvard

MW SysArc (2026) ‘Hydraulic Radius Calculator’, MW SysArc Tools. Published 21 July 2026. Available at: https://math.mwsysarc.com/geometry/hydraulic-radius-calculator (Accessed: 31 August 2026).

BibTeX and RIS records

BibTeX

@misc{mwsysarc_hydraulic_radius_calculator_2026,
  author = {{MW SysArc}},
  title = {Hydraulic Radius Calculator},
  howpublished = {MW SysArc Tools},
  year = {2026},
  url = {https://math.mwsysarc.com/geometry/hydraulic-radius-calculator},
  note = {Published July 21, 2026; accessed August 31, 2026}
}

RIS

TY  - ELEC
AU  - MW SysArc
TI  - Hydraulic Radius Calculator
T2  - MW SysArc Tools
PY  - 2026
DA  - 2026-07-21
Y2  - 2026-08-31
UR  - https://math.mwsysarc.com/geometry/hydraulic-radius-calculator
N1  - Published July 21, 2026
ER  -

Clear answers

Frequently asked questions

What does the Hydraulic Radius do?

Calculate hydraulic radius from flow cross-sectional area and wetted perimeter.

How does the Hydraulic Radius work?

The calculator applies c=a/b. Hydraulic radius divides flow area by wetted perimeter. This page evaluates the relationship directly.

What can I learn from the Hydraulic Radius?

It connects the mathematical rule to your chosen numbers and shows each calculation step. Change one input at a time to see how the result responds.

Does MW SysArc receive or store what I enter?

No. The calculation runs locally in your browser. MW SysArc does not receive or store your calculation inputs.

How should I use the result?

Use the steps to understand the method, then verify important school or professional work using the notation and rounding rules required in your setting.

Last reviewed . Calculations tested .

MW SysArc Certified