Keyboard Layout Size Calculator
Enter a layout family and plate thickness to get overall case width and depth, total key count, plate area and the bezel margin your case needs.
Tool Operation Area
Computed geometry
Based on the 19.05 mm key pitch standard. Allow 2-4 mm tolerance on production cases for chamfers, draft angles and weight inserts.
Working Principle
Mechanical keyboard geometry is built on a single constant: one key unit (1u) equals 19.05 mm of pitch, the spacing standard inherited from IBM and adopted by every Cherry MX compatible PCB. Because switch plates are drilled on that same grid, a layout's raw switch field is simply its width in units multiplied by 19.05 mm, and its depth is the number of rows multiplied by the same figure. A 60% layout is 15u wide by 5 rows deep, so the switch field measures roughly 285.75 mm by 95.25 mm; a full-size board is 22.5u by 6.5 rows. On top of that field the case adds a bezel on all four sides. Most gasket and tray mount cases use a 4 mm to 10 mm bezel, which is what the margin input controls, and the outer dimension is the switch field plus twice the bezel. Plate thickness does not change the footprint, but it changes stack height and stiffness: FR4 and aluminium plates in the 1.2 mm to 1.6 mm range are the common compromise between typing flex and stability, while thinner 1.0 mm polycarbonate flexes noticeably. The calculator adds plate thickness, switch body height above the plate (about 11.5 mm for MX), keycap height and case wall allowance to estimate the front height of the finished board. Key counts come from the standard row maps for each layout family, so the number reflects real production kits rather than a theoretical grid.
How to Use
- 01Pick your layout family. If your kit is described as 65% with a rotary encoder, choose 65% — the encoder occupies a key position and does not change the footprint.
- 02Set plate thickness. Read it from the vendor spec sheet; 1.5 mm is the default for aluminium, 1.2 mm for FR4 and polycarbonate.
- 03Set the case bezel you plan to use, per side. Low profile cases sit near 4 mm, chunky CNC cases near 10 mm.
- 04Read the outputs: switch field, outer case size, key count and estimated front height.
- 05Common mistake: measuring your desk mat against the switch field instead of the outer case size. Always use the outer figure for clearance planning.
FAQ
Why does my case measure slightly larger than the result?
Production cases include wall draft angles, chamfers and weight inserts. Treat the output as the design footprint and allow 2-4 mm of tolerance on each axis.
Does the key count include the spacebar as one key?
Yes. Every switch position counts once regardless of its unit width, so a 6.25u spacebar is one key with three stabilizer positions.
Where does the 19.05 mm figure come from?
It is 0.75 inch, the historical key pitch standard. Every MX compatible plate, PCB and keycap set is cut on this grid.
Can I use this for ortholinear or split boards?
Only as an approximation. Ortholinear grids share the 19.05 mm pitch, so multiply your own column and row count manually and use the bezel logic as-is.
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