Decide what must stay fixed
You cannot fix the wall width, number of frames, frame width, gaps and margins independently: those quantities must add up. Start with the real wall width. Choose a number of frames and a clear gap, then let the frame width be the result. Alternatively, choose a frame width and calculate the remaining space. Our calculator follows the first method, with equal left and right margins.
Use outside frame dimensions
A decorative frame has an outside size and a clear opening. The gap between two frames is measured between their outside edges. If a moulding has a visible face width of 3 cm, a 76.67 cm wide frame leaves a 70.67 cm wide inside opening. The face width is subtracted twice. The depth projecting from the wall is a different measurement and is not part of this calculation.
The horizontal formula
Outside frame width = [wall width − 2 × side margin − (columns − 1) × gap] ÷ columns. For a 300 cm wall, 20 cm side margins, 3 columns and a 15 cm gap, each frame is 76.67 cm wide. Check the total: 20 + 76.67 + 15 + 76.67 + 15 + 76.67 + 20 is approximately 300 cm. The small difference comes from display rounding; the calculator keeps the unrounded geometry.
The vertical formula
Outside frame height = [wall height − top clearance − bottom clearance − (rows − 1) × gap] ÷ rows. On a 240 cm high wall with 25 cm top and bottom clearances, two rows and a 15 cm gap, each frame is 87.5 cm high. Horizontal and vertical gaps use the same input in this planner. Choose one row when you want tall frames without a horizontal division.
When equal spacing is not the right answer
A door, a window or a fireplace may make a perfectly regular grid look awkward or cause a physical clash. The calculator flags intersections with the obstacle you enter; it does not claim the layout is appropriate for installation. Compare several frame counts and margins. Reject a design if a frame becomes too narrow for its moulding face. Equal arithmetic is a starting point, not a rule that every room must follow.