Rectangular board diagonal checker
The rectangular board diagonal checker gives the diagonal a true rectangle of your width and height should measure.
Result and working notes
Use 100% print scaling for this record. The sketch is not life-size and must not be used as a cutting pattern. Check measurements against the real materials.
Expected rectangular diagonal: 150 cm
Matching one diagonal alone does not prove a frame is square. Check both diagonals and the physical corners.
| Expected rectangular diagonal | 150 cm |
| Absolute difference from measured diagonal | 0 cm |
| Your tolerance comparison | Within your chosen tolerance |
Free to use. A free account saves, downloads and prints your results, with no card.
Use the square root of width squared plus height squared, then compare it with your measured diagonal. Adjust the numbers and check the live result before printing your measurement notes.
Last reviewed 3 October 2026.
Work out your display
- Measure the board, paper or existing item. Choose a single unit that matches the fields.
- Set width (cm), height (cm), measured diagonal (cm), your allowed difference (cm).
- Compare the live totals with the stated assumptions. Use a free account to download or print the measurement sheet.
How the estimate is calculated
Use the square root of width squared plus height squared, then compare it with your measured diagonal. Matching one diagonal alone does not prove a frame is square. Check both diagonals and the physical corners.
This utility supports the measuring and preparation work around a display. It provides plain quantities and dimension notes; custom lettering, bunting artwork, decorations and finished themed packs belong in the display maker.
Every result comes from the values you enter, with no model request or invented price.
Practical questions
How does rectangular board diagonal checker work?
Use the square root of width squared plus height squared, then compare it with your measured diagonal.
What should I check before using the result?
Matching one diagonal alone does not prove a frame is square. Check both diagonals and the physical corners. Start with measured values for width (cm), height (cm), measured diagonal (cm), your allowed difference (cm).
Is this display preparation tool free?
Yes. You can calculate and preview without signing in. Saving, downloading and printing need a free account, with no card.
Will this produce a finished display pack?
No. It prints calculation notes for rectangular board diagonal checker, rather than a design template or decorative artwork. When you want a finished board, lettering, bunting or decorations, the WallKiwi display maker designs them for you.
Tools for the next step
- Measuring and print estimatesUsable display board areaFind the working space left inside a board after reserving an equal edge on every side. Free in your browser, with printable notes you can save.
- Measuring and print estimatesDisplay border roll estimatorWork out how many rolls of edging you need for a rectangular board. Free in your browser, with printable notes you can save.
- Measuring and print estimatesBacking paper roll calculatorEstimate vertical strips and roll length for covering a board with backing paper. Free in your browser, with printable notes you can save.
- Measuring and print estimatesBacking sheet coverage calculatorCount rectangular paper sheets needed to cover a display surface in a regular grid. Free in your browser, with printable notes you can save.
Cite this tool
APA 7
WallKiwi. (2026, October 3). Rectangular board diagonal checker. https://wallkiwi.com/tools/rectangular-board-diagonal-checker
Harvard
WallKiwi (2026) Rectangular board diagonal checker. Available at: https://wallkiwi.com/tools/rectangular-board-diagonal-checker.
Ready to make your display?
Describe your display in a sentence and WallKiwi designs the board, lettering, bunting and cut-outs to match, ready to print on A4. Designs use credits, and a free account includes some each month.