Rhombus Area Calculator
From the two diagonals of a rhombus, get the area, the side length, and the perimeter — the three numbers that describe a diamond.
Two diagonals, three answers
Enter both diagonals and the calculator returns the area ((d1 × d2) ÷ 2), the side length, and the perimeter at once.
Keep units consistent
The diagonals are unit-agnostic — your answers come back in the same unit (squared for the area), so don't mix centimetres with inches.
What is a rhombus area calculator?
Diagonals in, full rhombus out
A rhombus area calculator turns two measurements — the two diagonals, the lines joining opposite corners — into the numbers that describe the whole shape: its area, the length of each equal side, and its perimeter. A rhombus is a "diamond": a parallelogram with four equal sides. Its diagonals cross at right angles and cut each other in half, which is exactly what makes the area formula so simple. That makes the calculator handy for tiles and floor patterns, kite frames, jewelry, road signs, and any geometry homework where a diamond shape shows up.
Enter both diagonals in any length unit to get the area, side length, and perimeter instantly.
Three short formulas, all built from the two diagonals d1 and d2.
area = (d1 × d2) ÷ 2The area is half the product of the diagonals. The side is found with Pythagoras from half of each diagonal — side = √((d1 ÷ 2)² + (d2 ÷ 2)²) — because the diagonals bisect each other at right angles, so each side is the hypotenuse of a right triangle. The perimeter is then simply 4 × side, since all four sides are equal.
Suppose you have a rhombus with diagonals of 6 and 8.
Area
(6 × 8) ÷ 2 = 48 ÷ 2 = 24 square units — the space inside.
Side length
√((6 ÷ 2)² + (8 ÷ 2)²) = √(3² + 4²) = √25 = 5 — each of the four sides.
Perimeter
4 × 5 = 20 — the distance once around the edge.
The three outputs answer three different everyday questions. The area (24 square units for diagonals 6 and 8) is the surface you cover — the glaze on a diamond tile, the fabric in a kite, the metal in a diamond road sign. The side length (5 here) is what you measure or cut along each edge, and because every side of a rhombus is equal you only ever need this single number. The perimeter (20) is the length of trim, frame, or border you wrap all the way around. A useful insight is that the diagonals always cross at right angles and bisect each other, which is why the side comes straight from the half-diagonals via Pythagoras — here the 3-4-5 right triangle gives a clean side of 5. When the two diagonals are equal, the rhombus becomes a square, so a square is just a special, upright rhombus.
The formulas are exact, but a couple of practical points are worth keeping in mind.
True rhombuses and consistent units
These formulas describe a perfect rhombus, where all four sides are equal and the diagonals meet at right angles. If a shape is a general parallelogram with unequal sides, use a parallelogram calculator instead. The diagonals are also unit-agnostic, so the answers are only meaningful if you keep one unit throughout: diagonals in centimetres give a perimeter in centimetres and an area in square centimetres, never a mix.