Equal-spacing calculator

Choose the outer-edge layout

Enter the clear opening width and the actual face width of one piece. Equal end gaps put the same open space before, between and after the pieces. Flush outer pieces place the first left edge and last right edge at the opening’s boundaries, leaving gaps only between pieces.

Fixed-count mode calculates the equal gap. Maximum-gap mode finds the smallest whole piece count that keeps each gap at or below your target; the resulting gap can be smaller than the target. The piece length is optional for this geometry. Enter it if you want to send the count and length to the cutting planner.

Formula and example

For opening S, piece width W and count N, equal end gaps use G = (S − N × W) ÷ (N + 1). Flush outer pieces use G = (S − N × W) ÷ (N − 1), requiring at least two pieces. Center-to-center spacing is W + G. Each position is measured from the same left reference edge.

Example: a 48 in opening with nine 2 in pieces and equal end gaps has 30 in of open space divided among ten gaps: each gap is 3 in. The first piece runs from 3 to 5 in, centered at 4 in. Centers repeat every 5 in through 44 in. With the same pieces flush at both ends, the eight internal gaps are 3¾ in.

Use unrounded positions when possible and mark from the reference edge rather than repeatedly adding a rounded step. Check the last position against the opening before fastening. This is geometric layout, not a check of structural loads, building-code clearances, mattress requirements or material movement. Choose the appropriate gap and installation method for your project.

Turn the layout into a cut list

Enter each piece’s finished length and send the layout to the linear cut-list calculator. It will carry the count and length across after you choose to load them. The board-foot calculator can tally purchased lumber afterward.