Triangle Land Area Calculator
Have a three-sided plot of land? Enter the length of each side in feet and this calculator returns the area in acres, square feet, square meters and hectares. Unlike a four-sided shape, a triangle’s area is exactly determined by its three sides.
Three Side Lengths → Area
Uses Heron's formula. All three sides are in feet.
How the Triangle Area Is Calculated
The calculator uses Heron’s formula, which finds a triangle’s area from its three side lengths alone — no angles or height needed. First compute the semi-perimeter s, then the area:
s = (a + b + c) ÷ 2 Area = √( s × (s − a) × (s − b) × (s − c) )
That result is in square feet; dividing by 43,560 gives acres. For the 300 / 400 / 500 ft example above, the area is 60,000 ft² = 1.3774 acres (it’s a right triangle, so you can check: ½ × 300 × 400 = 60,000).
Why Triangles Are Exact (and Four Sides Aren’t)
Three side lengths lock a triangle into a single, rigid shape — there’s only one possible area. That’s why this calculator is exact, while the four-sides acreage calculator can only estimate: a four-sided shape can flex into different areas with the same side lengths.
For a plot with more than three straight sides, split it into triangles and add the areas, or simply trace the whole boundary on a map.
Measure a Triangular Plot on a Map
If measuring the sides on the ground is awkward, trace the three corners on satellite imagery with the acreage calculator map — it computes the area from the corner coordinates directly, no side measurements required.
Frequently Asked Questions
How do I find the area of a triangular piece of land?
Measure the three side lengths and apply Heron's formula: compute the semi-perimeter s = (a + b + c) / 2, then area = √(s(s−a)(s−b)(s−c)). This calculator does it for you and converts the result to acres.
Can you calculate area from just three sides?
Yes. Three sides define a triangle exactly, so the area is unambiguous — unlike a four-sided plot, where the same side lengths can produce different areas.
How many acres is a 300 × 400 × 500 ft triangle?
It is 60,000 square feet, which is about 1.3774 acres.
What if my land has more than three sides?
Divide it into triangles, calculate each area and add them together — or trace the whole boundary on a map to measure it in one step.
Try Marea Today
Download Marea on iOS or Android and start measuring in seconds.
