Rhombus Area Calculator
The diagonals of a rhombus cross at right angles, so the area is their product over two. The side is the hypotenuse of the triangle formed by the half-diagonals.
Your numbers
Area
40cm²
Side length
6.403cm
Perimeter
25.61cm
Formula
Area = Diagonal 1 × Diagonal 2 ÷ 2
A square is a rhombus too — equal diagonals give you a square.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Diagonal 1 (cm)The length of the first diagonal. | 10 | 0 and up |
| Diagonal 2 (cm)The length of the second diagonal. | 8 | 0 and up |
Step by step
Quick reference table
Results when only Diagonal 1 (cm) changes and everything else stays put.
| Diagonal 1 (cm) | Area (cm²) | Side length (cm) | Perimeter (cm) |
|---|---|---|---|
| 5 | 20 | 4.717 | 18.87 |
| 7.5 | 30 | 5.483 | 21.93 |
| 10 | 40 | 6.403 | 25.61 |
| 15 | 60 | 8.5 | 34 |
| 20 | 80 | 10.77 | 43.08 |
What each result means
| Result | At default values |
|---|---|
| Area (cm²)The space a shape covers — length squared. | 40 |
| Side length (cm)One side of a regular polygon — they are all the same. | 6.403 |
| Perimeter (cm)The total length around the outside of a shape. | 25.61 |
Common mistakes
A square is a rhombus too — equal diagonals give you a square.
Glossary
- Diagonal 1
- The length of the first diagonal.
- Diagonal 2
- The length of the second diagonal.
- Area
- The space a shape covers — length squared.
- Side length
- One side of a regular polygon — they are all the same.
- Perimeter
- The total length around the outside of a shape.
Frequently asked questions
Q. How is Rhombus Area Calculator calculated?
Area = Diagonal 1 × Diagonal 2 ÷ 2 — The diagonals of a rhombus cross at right angles, so the area is their product over two. The side is the hypotenuse of the triangle formed by the half-diagonals.
Q. Can you walk through an example?
With Diagonal 1 10cm, Diagonal 2 8cm, the answer is Area 40cm².
Q. What do I need to enter?
Enter Diagonal 1, Diagonal 2. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Diagonal 1 (cm) moves the answer to Diagonal 1 (cm) 5 → Area (cm²) 20 and Diagonal 1 (cm) 20 → Area (cm²) 80. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
A square is a rhombus too — equal diagonals give you a square.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.