Measure the opening
Check the internal width at the front and back, and at the top and bottom. If the cabinet is uneven, use the smallest usable width and allow for assembly.
MAKE ROOM. MEASURE ONCE MORE.
A place for
everything.
Turn one opening into evenly spaced compartments. Account for the wood, check your boxes, and take a clear measurement sheet to the workshop.
Millimetres throughout · Nothing uploaded · Free to use
02 / YOUR MEASURING BOARDFRONT VIEW
Diagram proportions are accurate; displayed measurements are rounded to 0.01 mm. Use the full calculated values for layout and verify your physical opening.
03 / DIVIDER SET-OUT
Mark from the left.
Measure each divider’s left face from the inside left edge of the opening. All marks share that same reference, so rounding does not accumulate.
THE WORKSHOP NOTES
Good measurements make good spaces.
Count spaces, not boards
Three compartments need two internal dividers. The calculator subtracts those dividers and both edge allowances, then divides the remainder equally.
Leave room to reach
The box check compares outside width only, in the orientation you enter. A zero clearance fit is nominal: allow extra room for handles, tolerances and easy removal. Height, depth and load capacity are not checked.
Show the calculation
Compartment width = (internal width − 2 × edge allowance − (compartments − 1) × divider thickness) ÷ compartments.
This is a layout aid, not a structural or cutting plan. It does not calculate saw kerf, joints, panel height, material strength or fixing positions.