Keep calculation and display separate
One inch is exactly 2.54 centimetres. Our tools keep the geometry in centimetres internally, then convert the displayed inputs and results when you choose inches. You can plan in either system. Use the one that matches your measuring equipment and the material information you have, and label every number in a written sketch.
Decimal inches are not feet and inches
Enter 120 for a ten-foot wall when inches are selected. Do not enter 10.0 and expect the tool to interpret feet. A measurement of 12.5 inches is twelve and a half inches; it is not twelve inches and five sixteenths. The tools accept decimal dimensions and display the active unit next to each dimensional field.
Round only when you need a physical mark
A 300 cm wall divided into certain layouts can produce repeating decimals. The calculator keeps those values in its model, while the result table may show 76.67 cm. If three frames each display 76.67 cm, their displayed sum is 230.01 cm. That one-hundredth difference is display rounding, not a change in the wall. Do not repeatedly add rounded gaps to establish the final piece position.
Measure marks from one origin
Use the position table’s coordinates from the same wall edge. Check the final edge against the actual wall width. If your tape measure has coarser graduations than the displayed result, choose how to distribute that rounding across the real layout. A calculated number with two decimal places does not mean the material, wall or measurement is accurate to that precision.
Check units on the stock label too
A supplier may list a profile in millimetres and a stock length in metres while your wall is measured in inches. Convert each before entry. For example, a 30 mm face is 3 cm; a 2.4 m stock length is 240 cm. The tool does not read product labels or infer a nominal size. Verify actual face width and usable stock length before using a cutting estimate.