Formulas, without the guesswork.
Choose a relationship from the measurements you know. The variable names below belong to each calculator; a letter can have a different role in another method. π is evaluated using the browser’s full numerical constant, rather than replacing it with 3.14.
From an edge
Inputs: Edge a (length units).
From volume
Inputs: Volume V (cubic units).
From total surface area
Inputs: Total surface area S (square units).
From space diagonal
Inputs: Space diagonal d (length units).
Reading the notation
√ means a square root, ∛ means a cube root, and a superscript ² or ³ means a square or cube. Sine, cosine and tangent use angles converted from entered degrees. Where an inverse trigonometric function is used, its displayed angle is converted back to degrees. The ellipse perimeter is approximate; other formula labels describe the ideal mathematical model.
A face diagonal and a space diagonal are different measurements. Surface area is not measured in cubic units.
Reference reading: Cube at Wolfram MathWorld.