Carpet Seam and Drop Layout

ScopeRoll goods come one width only, so a room wider than the roll takes full drops plus a fill strip, and the real decision is which way to run it. A 30 x 20 ft room off a 12 ft roll takes 2 drops lengthwise (1 seam, 30 ft) or 3 crosswise (2 seams) -- the SAME 60 LF of carpet either way, so the seam count decides it, not the yardage. Reports drops, seam count and total seam length, the fill strip and whether it is too narrow to lay well, the cut length rounded up to whole pattern repeats so the pattern matches across a seam, and the actual waste once the drop geometry is counted (26% here, not the 5% allowance -- the geometry, not the trim). Rectangular room, no openings credited. Seams run with the traffic and the light, and nap direction must match across every drop; the installer's diagram governs.

Formula or tabledrops = ceil(across / roll width); fill strip = (across - (drops - 1) x roll width) x 12 in; seams = drops - 1; seam length = seams x run; cut length = ceil(run x 12 / repeat) x repeat / 12 when a repeat is given; running length = drops x cut length; order = running x (1 + waste) ; actual waste % = (ordered area - room area) / room area x 100. Both orientations are computed and the one needing less roll is reported, with the other shown for comparison.

Source and editionRoll-goods layout geometry. No table, no fitted constant, and no proprietary data; the only judgment values are the waste allowance and the minimum acceptable fill-strip width, both editable inputs.

Free accessElementary geometry - nothing here is licensed or tabulated.

What governsEstimate. AHJ and licensed professional govern.

API field namesroom_length_ft, room_width_ft, roll_width_ft, waste_pct, min_fill_strip_in, drops, seam_count, seam_length_ft, fill_strip_in, running_ft, order_running_ft, sy, waste_sf, waste_actual_pct, alt_drops, alt_seam_count, alt_running_ft

• Fixed roll width drops = ceil(across / roll width), remainder is a fill striproll-goods geometry
• Seam count drops - 1, each running the full length of the droproll-goods geometry
• Pattern repeat cut length rounds UP to a whole repeat so the pattern matches across a seamstandard patterned-goods practice
• Orientation both computed; the lower running length reported, the other showncomputed, not assumed
• Minimum fill strip 6 in default, editable; a narrower strip is flagged as poor practiceeditable judgment input
• Scope rectangular room, no openings, stairs, or transitions; seam placement is the installer'sstated scope limit