Useful for laying out a frame, slab corner or rectangular area with a tape. Compare the measured diagonal with the target for the two leg lengths.
- Side A and side B
- The two adjoining straight legs measured from a common corner.
One mode: the app calculates the diagonal of an assumed right angle. It does not read a measured diagonal or return an angle-error assessment.
- The required diagonal, alongside the two entered sides.
Two legs measured from the same corner.
| Quantity | Value |
|---|---|
| Side A; side B | 3 m; 4 m |
| Target diagonal | 5 m |
Diagonal = √(A² + B²). Match the measured endpoints and plane to the two legs used in the calculation.
Use metric or imperial lengths consistently and keep extra precision until the final display. Rounded diagram labels are not a measuring tolerance.
A matching diagonal is useful evidence for those three lengths. It does not by itself verify every corner, parallel side or level of an entire structure. No allowance is added.
Why compare both diagonals of a rectangle?
It helps check the full layout along with side lengths. This calculator supplies a theoretical diagonal; the field measurements remain yours.
Can I use feet and inches?
Yes. Keep both sides in the selected system and read the displayed diagonal in its labelled unit.
- Why compare both diagonals of a rectangle?
- It helps check the full layout along with side lengths. This calculator supplies a theoretical diagonal; the field measurements remain yours.
- Can I use feet and inches?
- Yes. Keep both sides in the selected system and read the displayed diagonal in its labelled unit.
A separate example in feet
A different physical size using the same method. This is not a conversion of the metric example above. Select the matching unit system in the app.
- Side A
- 6 ft (72 in)
- Side B
- 8 ft (96 in)
- Diagonal
- 10 ft (120 in)
ft means feet; in means inches. Use the same endpoints and plane as the side measurements shown in the diagram.
Measurements, units and material terms
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