Incircle Radius Calculator
Incircle r=Δ/sforactualstrictnondegeneratetrianglesides, notexcircle or radius from one leg.
Description
A triangle's inradius equals its area divided by its semiperimeter.
A triangle's inradius equals its area divided by its semiperimeter.1
This tool uses three valid side lengths and Heron's area without calculating an excircle radius.
When to use Incircle Radius Calculator
This tool uses three valid side lengths and Heron's area without calculating an excircle radius.
How to use Incircle Radius Calculator and how it works
- Prepare side a, side b, side c, using the input definitions and matching units below.
- Enter the required fields and run Incircle Radius Calculator.
- Read result.value using the units, signs and ordering explained below.
- Correct any rejected inputs and rerun; interpret the result within the stated model and its assumptions.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| sideA | Side A. Use the units and matching context stated in the calculation below. | number | Required; strictly positive; finite; other constraints below |
| sideB | Side B. Use the units and matching context stated in the calculation below. | number | Required; strictly positive; finite; other constraints below |
| sideC | Side C. Use the units and matching context stated in the calculation below. | number | Required; strictly positive; finite; other constraints below |
Require positive side lengths satisfying all strict triangle inequalities. Use Heron's formula for positive area and divide by semiperimeter. Return the inradius in the input length unit; degenerate triangles are errors.
s=(a+b+c)/2; area=sqrt(s*(s-a)*(s-b)*(s-c)); inradius=area/s Apply the input ordering, units and branch conditions stated above.
| Output field | Meaning | Value type |
|---|---|---|
| result | Object containing the calculated or selected fields below. | object |
| result.value | Geometric length in the supplied radius, side or curve-scale unit. | number |
{
"input": {
"sideA": 3,
"sideB": 4,
"sideC": 5
},
"output": {
"result": {
"value": 1
}
}
}Limitations and assumptions
The calculation uses the supplied observations and model inputs. It does not collect measurements, select a reference population or coefficient, or establish that the model applies to the actual case. The stated branch conditions and output units remain part of the result.
All fields require explicit values. Unexpected fields, wrong types, nonfinite numbers and sparse arrays are rejected. Alignment, bounds and supported-token rules are explained above; extremely large inputs or nonfinite results can also fail. Input errors differ from successful false comparisons, unavailable-domain flags and empty match lists.
Alternative or Complementary methods
Use Morley Triangle Calculator for a complementary operation: The first interior Morley triangle is formed by adjacent interior angle trisectors of a nondegenerate triangle.
Use Fermat Point Triangle Calculator for a complementary operation: The Fermat point minimizes total Euclidean distance to the vertices of a nondegenerate triangle.
References
-
Incircle Radius Calculator — tool.io
Similar or alternative tools
- Morley Triangle Calculator
The first interior Morley triangle is formed by adjacent interior angle trisectors of a nondegenerate triangle.
- Fermat Point Triangle Calculator
The Fermat point minimizes total Euclidean distance to the vertices of a nondegenerate triangle.