CalcaTools

Triangle Calculator

A Triangle Calculator is a free online tool that solves triangle area calculator using triangle area calculator, triangle angles, law of sines. Students, teachers, and engineers use it to check homework, prep for exams, and verify hand calculations.

Last updated: June 2026 · Free · No sign-up required

Results

Enter values above and click Calculate to see your result instantly.

Quick reference

NeedFormula
Area from base/heightA = 1/2bh
Right triangle hypotenusec = √(a²+b²)
Perimetera+b+c
Angle sumA+B+C = 180°

functions Shows the working, not just the answer

For students and teachers, the final number is only half the value. Every math tool here exposes the formula it applied, the intermediate steps, and the rounding rule, so you can follow along, check your homework, or use the answer in a proof or report with confidence.

calculate Accurate to the spec

Calculations use 64-bit floating point with sensible rounding for the domain (currency to 2 decimals, percentages to 4 decimals, algebra to 6 significant figures). Where exact rational arithmetic matters — fractions, factorials, simplification — we use a dedicated BigNumber path so 1/3 + 1/6 returns ½, not 0.49999.

school Free for classroom use

Educators are welcome to link to any math calculator on CalcaTools from a class site, Google Classroom, or worksheet. The pages are mobile-friendly, free, ad-supported (so we can keep them free) and have no sign-up wall — students just click and use them in class or at home.

tips_and_updates Pair with the spoke articles

Below the calculator we link a small set of plain-English explainer pages — "What is a percentage?", "Why does PEMDAS matter?", and so on. They cover the underlying concept in 4–6 short paragraphs. Read those before the calculator if the topic is new, or after if you want the extra context.

Interpretation guide

Triangle typeClue
RightOne 90° angle
IsoscelesTwo equal sides
EquilateralThree equal sides and 60° angles

lightbulb Example — a right triangle with legs 3 and 4

By the Pythagorean theorem the hypotenuse is √(3² + 4²) = √25 = 5. The area is ½ × base × height = ½ × 3 × 4.

Result: Hypotenuse = 5, area = 6 square units.

What this means: This is the classic 3-4-5 right triangle — any triangle with sides in that ratio has a 90° angle.

Formula & methodology

Formula: Area = 1/2bh; a² + b² = c² for right triangles

Triangle solving depends on known inputs. Right triangles use Pythagorean relationships; general triangles may require law of sines or cosines.

Frequently asked questions

How do I use the triangle calculator?
Enter the requested values, review the instant result, then compare the reference table and interpretation guide below the calculator. Adjust one input at a time to see which assumption changes the result most.
What formula does the triangle calculator use?
The calculator uses Area = 1/2bh; a² + b² = c² for right triangles and standard unit conversions or finance/statistics conventions where applicable.
Is the triangle calculator accurate?
Results are estimates based on the values entered; check source data and assumptions before making decisions.
Why do my results differ from another calculator?
Different calculators may round differently, include extra assumptions, or use a different input frequency. Match the units, dates, tax assumptions, and rounding method before comparing outputs.