How this calculation works
At 90° the rhombus is a square and both diagonals are equal.
THE FORMULA
Diagonal lengths = 2s cos(θ/2) and 2s sin(θ/2)A worked example
Side 5 and angle 60° produce diagonals 5√3 and 5.
Good to know
Use an interior angle strictly between 0° and 180°.
Reference: OpenStax Algebra and Trigonometry, Trigonometric Applications (opens in a new tab) ↗
Read the result
Recover the two diagonal lengths from a side and an interior angle.
The primary result is labeled “Long diagonal”. Keep the input definitions in view when comparing this result with another method.
Try a related calculation
Use an interior angle strictly between 0° and 180°.
For a related exercise, try the circle calculator.
A few questions, answered
How can I check the default inputs by hand?
Side 5 and angle 60° produce diagonals 5√3 and 5.
Which rule does this calculator apply?
Diagonal lengths = 2s cos(θ/2) and 2s sin(θ/2)