Triangle Area Calculator
Triangle area calculator works out Area and Area unit from Length / base / side a, Width / second base / side b and Perpendicular height. The default figures on this page give area of 30; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
4 steps
- Shape: Triangle (base and height). Dimensions are in m.
- Formula: A = (1/2) x base x height.
- Area = 30 m2.
- In SI: 30 m^2 (= 322.91731250129175 sq ft).
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
What the triangle area calculator calculates
Calculates the area and perimeter of any named plane shape - square, rectangle, triangle, parallelogram, rhombus, kite, trapezoid, circle, semicircle, ellipse, annulus, sector, segment or regular polygon - in any length unit, with the result convertible to any area unit.
How to use this triangle area calculator
Enter Length / base / side a, Width / second base / side b, Perpendicular height and Side c. Area updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Area, Area unit and Area in square metres.
The method follows CRC Standard Mathematical Tables and Formulae, Geometry: areas and perimeters of plane figures, Weisstein, Eric W. "Area", MathWorld, S. Ramanujan, "Modular equations and approximations to pi", Quart. J. Pure App. Math. 45, 350-372, equation (2) for the ellipse perimeter and NIST Special Publication 811, Guide for the Use of the International System of Units (unit conversions).
What you can compare
Change one input at a time to see how it affects Area, Area unit and Area in square metres. The inputs you can vary are Length / base / side a, Width / second base / side b, Perpendicular height, Side c, Radius and Inner radius.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
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Frequently asked questions
What information do I need for the triangle area calculator?
You need Length / base / side a, Width / second base / side b, Perpendicular height, Side c, Radius, Inner radius, Diagonal p and Diagonal q. The page opens with default figures that give area of 30, so you can see the scale before entering your own.
What does this triangle area calculator show?
It shows Area, Area unit, Area in square metres, Area in square feet, Perimeter, Perimeter unit, Shape and Formula used, with the working and any warnings for your entries.
Can I check how the triangle area calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.