SOLVE · DRAW · UNDERSTAND
Triangle Calculator
Enter exactly three known values — with at least one side — and solve SSS, SAS, ASA/AAS or the full SSA ambiguous case. Then inspect the geometry, not just the answer.
5 casesSSS to SSA
2 solutionswhen SSA allows it
localno upload
TRIANGLE WORKBENCH
Start with what you know
Standard notationside a ↔ angle A · b ↔ B · c ↔ C
Enter exactly three values. Fractions such as 3/4 work. Three angles alone define shape but not size.
RIGHT TRIANGLE QUICK SOLVER
Enter exactly two sides
Here c is the hypotenuse. Leave the missing side blank.
MISSING SIDE—
Uses the Pythagorean theorem, then returns the full triangle.
Three sides
—A = ½ab sin C
—COMPLETE TRIANGLE
No solved triangle yet.Every side, angle and derived measurement
Sides & angles
- a
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- b
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- c
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- A
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- B
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- C
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Size
- Perimeter
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- Semiperimeter
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- Area
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- Inradius r
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- Circumradius R
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- Classification
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Altitudes
- hₐ
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- hᵦ
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- h꜀
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Medians
- mₐ
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- mᵦ
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- m꜀
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Angle bisectors
- ℓₐ
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- ℓᵦ
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- ℓ꜀
- —
All derived lengths use the same unit as your sides.
SCALED DIAGRAM
See the solved geometry
Diagram is scaled to the solved side ratios; labels show rounded values.
Method steps
- Enter exactly three known measurements.
Built-in checkstriangle inequality · angle sum · positive lengths · SSA ambiguity
DAILY TRIANGLE
One geometry check per UTC day
Same triangle for everyone on the date. Estimate the requested measurement, then check your reasoning.
TODAY'S TRIANGLE—
Which answer is correct?
Choose an answer.
Methods, notation & scope
Which method gets used?
SSS uses the law of cosines. SAS finds the opposite side first. ASA/AAS finds the third angle then uses the law of sines. SSA is tested for zero, one or two valid triangles instead of silently choosing one.
Derived geometry
Area comes from Heron or an equivalent trig formula. The inradius is K/s; the circumradius is abc/(4K). Altitudes, medians and internal angle bisectors are computed from the solved side lengths.
Right triangles and area
The focused right-triangle tab solves one missing side from the other two. The area lab keeps base-height, Heron and two-sides-plus-angle formulas available without forcing a full solve.
Privacy & limits
Everything runs locally in this browser. This solver models ordinary non-degenerate Euclidean plane triangles; it is not a surveying/geodesy engine and does not account for measurement uncertainty.