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Instant result
Enter the data and press the button to do the calculation.
Online Calculator
Triangle calculator from three sides
Enter the three side lengths to calculate area with Heron’s formula and angles with the law of cosines.
Information
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Local processing
The values are processed directly in your browser.
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Free
No registration, external API or subscription required.
Frequently asked questions
What data do I need?
The lengths of the three sides.
How is the area calculated?
With Heron's formula.
How are the angles calculated?
Using the law of cosines.
What's the calculator worth?
Check that the three sides satisfy the triangle inequality.