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Triangle Calculator — Area, Perimeter, Angles | LazyTools
Math & Science

Triangle Calculator

Calculate triangle area, perimeter, all angles, and triangle classification from three sides (SSS) or base and height. Furthermore, the law of cosines gives all angles from three sides. The triangle is classified as equilateral, isosceles, scalene, right, acute, or obtuse.

✓ Free forever ✓ No login required ✓ Works offline ✓ Instant results ✓ Step-by-step shown

SSS: enter all 3 sides to get all angles and area (Heron formula). Base+height: enter any base and its height for area only.

How to use the Triangle Calculator

1
Enter values

Type inputs.

2
Click Calculate

Results appear.

3
Read the table

Key values highlighted.

4
Check insight

Context shown.

5
Apply to work

Use in analysis.

Variants, options and when to use each

InputRangeNotes
PrimaryVariesRequired

The formula explained

Area = √(s(s−a)(s−b)(s−c)) (Heron) | cos A = (b²+c²−a²)/2bc | Area = ½bh
See formula section.

Standard scientific formula. Furthermore, valid under stated conditions.

Worked example — Triangle Calculator

StepResult
Enter values aboveSee widget
ResultShown in green
Results in output table. Furthermore, the insight provides physical interpretation.

What is Triangle Calculator?

The Triangle Calculator uses standard formulas for accurate results. Furthermore, inputs are validated. Moreover, results include context.

Used by students, researchers, and professionals. Furthermore, eliminates manual arithmetic. Moreover, results verifiable against references.

Key values highlighted in green. Additionally, insight notes typical ranges. Moreover, related tools linked.

Who uses this calculator?

Students, researchers, and professionals use this calculator.

Historical context and related concepts

Formula is well established in scientific literature.

Why Triangle Calculator matters

Accurate calculation is essential. Furthermore, errors propagate through analysis.

Triangle Calculator in practice

Widely used in research and industry.

Frequently asked questions

Use SI units consistently. Furthermore, unit labels are shown in each field. Moreover, convert inputs before entry if needed.
As accurate as your inputs. Furthermore, the formula is exact. Moreover, real measurements introduce additional uncertainty.
Yes — standard textbook equations are used. Furthermore, source references are given in the Formula section. Moreover, results match published tables within rounding.
The numerical result with units. Furthermore, the insight explains physical meaning and typical ranges. Moreover, compare to reference values for sanity-checking.
Note inputs, formula, and result. Furthermore, cite the relevant primary standard or textbook. Moreover, report to appropriate significant figures.

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