Triangle area calculator
Fill in what you know and leave the unknown box empty — it works out whichever one is missing. Nothing is uploaded; the arithmetic happens in your browser.
The formula
A = ½bh
Where this usually goes wrong
h is the perpendicular height to the base you chose, not the slanted side.
Worked example
A base of 10 and height of 6 gives an area of 30.
Those numbers are already in the boxes above — press Work it out to see it, then change them for your own.
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