Setting out
Square a rectangular set-out
- where
- target diagonal (m)
- length (m)
- width (m)
- difference between measured diagonals (mm)
- measured diagonals 1 and 2 (m)
Explain this equation
Checks whether a rectangular set-out is square. It gives the target diagonal for the planned length and width and compares the two diagonals you have actually taped.
L and W are the intended sides in metres. dt is the theoretical diagonal of a perfect rectangle. d1 and d2 are the two diagonals you measured, corner to corner. Δ is how far apart they are, in millimetres. The calculator also shows how far each measured diagonal is from dt.
The diagonal is the hypotenuse of a right-angled triangle, so Pythagoras gives dt = √(L² + W²). If the corners are out of square, one diagonal grows and the other shrinks. The × 1000 turns metres into millimetres.
A 4 × 3 m set-out should measure 5.000 m on both diagonals. Readings of 5.000 and 5.010 m give a 10 mm difference.
Watch out: equal diagonals only prove you have a rectangle of some size. Check the side lengths and position as well.
Find the target diagonal and compare two measured diagonals.
Enter your values to see the result.
Good to know
Equal diagonals alone do not prove every side or corner is correct. Check side lengths, right angles, datum and position as well.
Sources
- Geometry / arithmetic
This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.