About

Miscalculating curtain fabric leads to panels that gap, puddle unevenly, or require costly re-orders. The relationship between window width, heading type, and fullness ratio (F) determines total fabric consumption. A pencil pleat heading demands F = 2.0 - 2.5, while an eyelet heading needs only 1.5 - 2.0. Ignoring pattern repeat (R) on printed fabrics wastes 10 - 30% more material than planned. This calculator derives the exact number of fabric widths, adjusted cut length, and total yardage required.

The tool assumes standard selvedge trim of 2cm per side and accounts for pre-wash shrinkage only if specified. Results approximate retail fabric bolt consumption. For fabrics with directional nap (velvet, chenille), add 10% to the total. Pattern matching across multiple widths requires alignment at every seam, which this calculator handles via the repeat adjustment formula.

Formulas

The total fabric width required across all panels is the product of the track or pole width and the fullness ratio:

W_total = W_track × F

The number of fabric widths (drops) needed is determined by dividing total width by the usable fabric width (bolt width minus selvedge):

N_widths = ceil(W_totalW_fabric − 4cm)

The raw cut length per width is the sum of the finished drop length plus allowances:

L_cut = L_finished + A_top + A_bottom

When the fabric has a pattern repeat R, each cut must be rounded up to the nearest repeat multiple:

L_adjusted = ceil(L_cutR) × R

Total fabric consumption:

M_total = N_widths × L_adjusted

Where: W_track = track/pole width, F = fullness ratio, W_fabric = fabric bolt width, L_finished = desired finished curtain length, A_top = top heading allowance, A_bottom = bottom hem allowance, R = vertical pattern repeat distance, M_total = total linear fabric required.

Reference Data

Heading Type	Fullness Ratio (F)	Top Allowance	Bottom Hem	Best For
Pencil Pleat	2.0 - 2.5×	10cm	15cm	Traditional, formal rooms
Pinch Pleat (Triple)	2.0 - 2.5×	10cm	15cm	Elegant drapery
Goblet Pleat	2.0 - 2.5×	12cm	15cm	Luxury, stationary panels
Eyelet / Grommet	1.5 - 2.0×	5cm	15cm	Modern, casual
Tab Top	1.5 - 2.0×	5cm	15cm	Casual, cottage style
Rod Pocket	2.0 - 2.5×	8cm	15cm	Sheers, café curtains
Wave / Ripplefold	2.0 - 2.4×	3cm	10cm	Contemporary, motorized tracks
Box Pleat	2.5 - 3.0×	10cm	15cm	Valances, formal
Cartridge Pleat	2.0 - 2.5×	10cm	15cm	Heavy fabrics
Inverted Box Pleat	2.5 - 3.0×	10cm	15cm	Structured valances
Flat Panel (No Pleat)	1.0×	5cm	10cm	Roman shades, decorative flat
Smocked	2.5 - 3.0×	12cm	15cm	Decorative, textured

Frequently Asked Questions

Every fabric width must be cut so the pattern aligns at the seam. If your cut length is 245cm and the repeat R is 64cm, the adjusted cut becomes ceil(245 ÷ 64) × 64 = 256cm. Over 6 widths, that adds 66cm of waste. Larger repeats increase waste proportionally.

Sheers typically require F = 2.5 - 3.0 to avoid transparency when gathered. Heavy fabrics (velvet, brocade) work at F = 1.5 - 2.0 because excessive gathering creates bulk at the heading and impedes stacking.

Always measure the track or pole width, not the window opening. Poles typically extend 15 - 20cm beyond each side of the window. If you input the bare window opening, your curtains will not cover the wall return and light will leak at the edges.

Natural fibers (cotton, linen) shrink 3 - 5% lengthwise. Pre-wash before cutting, or add 5% to L_finished. Polyester and blended synthetics typically shrink under 1% and can be cut to calculated length directly.

A "width" is one cut of fabric at the bolt width (e.g., 140cm). A "panel" is the finished curtain hung on one side of the window. One panel may consist of multiple widths sewn together. For a 300cm track at F = 2.0, you need 600cm total, which is about 4.4 widths of 140cm fabric, rounded to 5 widths split across 2 panels.

Yes. Input the finished length you desire: sill length (to the windowsill), below sill (15cm below), floor length (1cm above floor), or puddle (5 - 15cm pooling on the floor). The calculator adds heading and hem allowances on top of whatever length you specify.