Rhombus Area Calculator
The area of a rhombus from its two diagonals — half their product, with the side length and perimeter alongside.
A rhombus is a parallelogram with all four sides equal — a pushed-over square.
How the rhombus area calculator works
A rhombus is a parallelogram with all four sides equal — a pushed-over square. Its diagonals cross at right angles and bisect each other, which is what makes the area exactly half their product. Each side is then found by Pythagoras from the two half-diagonals.
Formula: square a²; rectangle ab; triangle ½bh; circle πr²; parallelogram bh; trapezoid ½(a+b)h; ellipse πab
Worked examples
| Inputs | Area | Note |
|---|---|---|
| Diagonals 10 and 6 | 30 | area 30, side 5.83 |
| A square turned 45° | 32 | 32 |
| A long thin rhombus | 40 | 40 |
FAQFrequently asked questions
What is the area of a rhombus?
Half the product of its diagonals: ½ × d₁ × d₂.
Why does that work?
The diagonals cross at right angles, dividing the rhombus into four right triangles that reassemble into a rectangle of half the size.
How do I find the side?
Pythagoras on the half-diagonals: √((d₁/2)² + (d₂/2)²).
Is a square a rhombus?
Yes — a rhombus whose angles are all right angles.
Can I use base times height instead?
Yes, since a rhombus is a parallelogram. Use the diagonals when those are what you can measure.
Where these figures come from
- NIST Digital Library of Mathematical Functions — reference definitions for elementary and special functions
- Wolfram MathWorld — definitions and formulas for every topic on this page
- NIST/SEMATECH e-Handbook of Statistical Methods — the statistical formulas (mean, variance, z, confidence intervals, sample size)
- Common Core State Standards — Mathematics — the terms and methods taught in US schools
Last checked: September 2026. Formulas are fixed by mathematics and do not change with tax years or regulations.