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Triangle calculator
Calculate area, perimeter and all three angles from the side lengths.
Numbers and dates
Text
Browser only
Runs locally in your browser. Your files, pasted content and generated output are not uploaded. Reset clears this tool’s working data.
This tool needs JavaScript. If it does not load, refresh the page and try again.
How to use this tool
- Enter values using decimal points and choose the operation or assumptions shown.
- Select Calculate and review the numerical result and its stated conventions.
- Download the result or amortization schedule when available. Reset restores the example inputs.
Examples
Sides 3, 4 and 5 give area 6, perimeter 12 and a 90-degree angle opposite side c.
Limitations
- Runs locally. Decimal calculations use floating-point arithmetic, rounded to 12 significant digits; monetary displays use two decimals. Exact integer and fraction results are labelled separately.
- All dimensions must use the same length unit, from 1e-12 to 1e12. Area and volume use the square or cube of that unit.
- Uses side-side-side input and rejects degenerate triangles. Angles are in degrees, opposite the matching side letter. Very thin triangles are sensitive to input precision.
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