SettingsSettings for this calculationUS
The long dimension of the rectangle being set out.
Use the dimension the governing rulebook publishes for the level of play, measured to the outside of the line unless that rulebook says otherwise. Where a hall carries more than one sport, set out the dominant court first and hang the others off its control line rather than off each other.
The short dimension of the same rectangle.
Walk the run-offs before you commit to it. A hall that measures fine on paper can still leave you short behind a baseline once retractable seating, a door swing and wall padding are in, and shifting the whole rectangle along its long axis at setting-out stage costs ten minutes rather than a re-coated bay.
How far the 3-4-5 right-angle triangle is scaled up before it is struck.
The three numbers are read in whichever unit you are working in — the toggle above decides whether the legs come back in metres or in feet, and the ratio makes the right angle either way. Scale matters more than tooling: an error at the mark magnifies all the way down the sideline, so a triangle struck at three units is worthless over a court of thirty, and the right angle is best set at the court centre so any residual error is shared between the two halves.
How far one corner may sit off its true position along the long axis.
This is not the rulebook's dimensional tolerance; it is the skew you are willing to accept, which should be tighter. A rectangle whose sides are all within tolerance can still read as visibly crooked, because what the eye picks up is the difference between the diagonals rather than the absolute length of either.
Expected diagonal
104.2 ft
Equal diagonals prove the figure is a rectangle, and only then do the side dimensions mean anything. Hold the two within the difference shown rather than within the rulebook's dimensional tolerance.
- Diagonal difference at the permitted offset
- 0.35 in
- Short leg of the squaring triangle
- 12 ft
- Long leg of the squaring triangle
- 16 ft
- Hypotenuse of the squaring triangle
- 20 ft
- Perimeter of the rectangle
- 282 ft
They open the calculator with your figures already in it
Court Diagonal and Squaring Triangle Calculator: 104 ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- The diagonal of a rectangle is the square root of length squared plus width squared. Where one end is displaced by an offset, the two diagonals become the roots of (length + offset)² + width² and (length − offset)² + width², and their difference is what a tape reads as out of square.
- ITF Rules of Tennis — court dimensions, which publish the corner-to-corner diagonal alongside the sides as a check dimension for exactly this reason
- FIBA Official Basketball Rules, court dimensions (28 m by 15 m for a full-size court); FIVB Official Volleyball Rules (18 m by 9 m); BWF Laws of Badminton (13.4 m by 6.1 m for doubles)
- The squaring triangle is a scaled 3-4-5, whose numbers are read in whatever unit the crew is working in — the ratio is what makes the angle, not the unit.
Inputs used
- Court Length
- 92 ft
- Court Width
- 49 ft
- Squaring Triangle
- 12-16-20 — full-size courts
- Permitted Corner Offset
- 0.2 in
Intermediate steps
- Diagonal difference at the permitted offset
- 0.35 in
- Short leg of the squaring triangle
- 12 ft
- Long leg of the squaring triangle
- 16 ft
- Hypotenuse of the squaring triangle
- 20 ft
- Perimeter of the rectangle
- 282 ft
Confidence note: Equal diagonals prove the figure is a rectangle, and only then do the side dimensions mean anything. Hold the two within the difference shown rather than within the rulebook's dimensional tolerance.
What this calculation does not cover
- A tape reading is a temperature reading as well. Use one tape at one tension for both diagonals, and note the surface temperature outdoors.
- This proves the rectangle. Arcs, keys and circles are struck from points established off it and carry their own checks.
Part of a bigger job
This trade is one line of a job takeoff. Run the whole job and every other trade comes back with it, off the same measurements.
also measures19 other trades
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-08-30 · in the site-wide review of 2026-09-06 · v1.0.0
Regulatory standards & verification citations4
- The diagonal of a rectangle is the square root of length squared plus width squared. Where one end is displaced by an offset, the two diagonals become the roots of (length + offset)² + width² and (length − offset)² + width², and their difference is what a tape reads as out of square.
- ITF Rules of Tennis — court dimensions, which publish the corner-to-corner diagonal alongside the sides as a check dimension for exactly this reason
- FIBA Official Basketball Rules, court dimensions (28 m by 15 m for a full-size court); FIVB Official Volleyball Rules (18 m by 9 m); BWF Laws of Badminton (13.4 m by 6.1 m for doubles)
- The squaring triangle is a scaled 3-4-5, whose numbers are read in whatever unit the crew is working in — the ratio is what makes the angle, not the unit.
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.
Tools and safety for this job
To set out and check dimensions. Generic types, no brands, no prices.
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Essential
String line and pins
Tape measure
Recommended
Chalk line
Optional
Laser level
Also needed as materials: chalk refill.
what each site-management tool is for, and the spec that decides which to buy where one does.