One consistent unit
The calculators use centimetres internally and convert inches using exactly 2.54 cm per inch. Displayed results are rounded to two decimal places; calculations use unrounded values. Toggling input units displays up to six decimal places.
Wall panel geometry
Outside width = (wall width − 2 × side margin − (columns − 1) × gap) ÷ columns. Height uses the same formula with top and bottom clearances. The inside opening subtracts twice the moulding face width. Obstacles are tested against the four physical strips, not the empty centre.
Stock allocation
Each finished long-point length receives the extra allowance at both ends. Blanks are sorted longest first and placed in the first stock length with sufficient space. Two end trims are removed from every stock length and a kerf is charged for every blank, including the last. This conservative first-fit decreasing estimate is not a guarantee of minimum waste. Defects, pattern matching, spare pieces and installation mistakes are excluded.
Batten geometry
There is one more batten than the number of bays. Clear gap = (width − batten count × face width) ÷ bay count. Each left edge is an integer multiple of clear gap plus face width. Rails are excluded.
Gallery geometry
The group is centred horizontally. Its top edge is wall height minus group centre above floor minus half the group height. A single centred support is located half a frame width from the frame’s left edge and the entered offset below its top.
What these tools cannot establish
They cannot verify your measurements, wall condition, fixing capacity, hidden services, product suitability or safe installation. A drawing is not a full-size template. If a result conflicts with the physical project, stop and recheck the inputs and assumptions.
Corrections
If you find an arithmetic or editorial issue, use the contact page and include the tool, units, inputs and expected result.