TrimTally / Guide
Use actual board width in trim calculations
Learn why measured board width matters for decorative spacing and how small width differences change the final layout.
Measure the board you will install
A product name or nominal size is not a reliable input for visible spacing. Measure the actual face width of the material you intend to use, in the orientation it will be fixed. Profiles, milling and product types differ; there is no single conversion that covers every trim product.
Small differences repeat across the wall
Suppose a 122-inch wall has seven flush-edge boards. At 2 inches wide, the gap is 18 inches. If the boards actually measure 1.75 inches, they cover 12.25 inches, leaving 109.75 inches across six gaps, or about 18.29 inches each. Using the wrong board width changes every mark.
Keep units consistent
Use inches for every dimension or millimetres for every dimension. There are exactly 25.4 millimetres in one inch. Our unit selector converts dimensional inputs; a board count remains a count. Decimal inches are supported, so enter 1.5 for one and a half inches rather than typing 1/2 into a number field.
Choose a repeatable measurement
Check more than one piece if the material varies, and record how you measured the face. If a decorative profile has a narrow flat section but a wider overall face, decide which outer edge defines the spacing and use that consistently.
Plan quantities separately
A combined linear length is not a purchasing list. Stock lengths, usable offcuts, mitres, saw kerfs, defects and rails determine what you need to buy. The layout calculator intentionally does not infer those allowances from a wall diagram.
Questions, answered
Can I use the labelled width from a store listing?
Use it only if it explicitly gives the actual dimension and it matches the material you receive. Verify important dimensions yourself.
Does the calculator accept fractions?
Use decimal equivalents: ¼ is 0.25, ½ is 0.5 and ¾ is 0.75.