Curtain Fabric Calculator

Heading Types and How They Change Fabric Requirements

The heading style you choose has a bigger effect on total fabric than any other single decision. Each heading type requires a different fullness ratio — the amount of fabric gathered per unit of track or pole width — and that ratio multiplies across every panel.

• Pencil pleat (2 to 2.5 times fullness) — the most common curtain heading in the UK and a popular choice everywhere. Fabric is gathered into narrow, regular pleats using heading tape. Two times fullness is standard; 2.5 times gives a richer look.
• Pinch pleat (2.5 times fullness) — groups of two or three pleats pinched together at regular intervals. These create a more tailored, structured look and require slightly more fabric than pencil pleat.
• Eyelet / grommet (2 times fullness) — metal rings punched through the fabric header create deep, even folds. Popular for modern and casual settings. The folds are bold and regular.
• Tab top (1.5 times fullness) — fabric loops or tabs are sewn to the top of the curtain and threaded onto the pole. Because tab tops hang flat between the tabs, they need the least fabric.
• Goblet pleat (2.5 to 3 times fullness) — each pleat is shaped into a goblet or tulip form, stuffed with wadding. This is a high-end heading that uses the most fabric. For more on how fullness ratios are applied, see our guide to calculating curtain fabric.

The calculator applies your chosen fullness ratio to the total track width, then divides by fabric width to determine how many drops (lengths of fabric) you need per panel.

How to Calculate Curtain Fabric

The process follows a logical sequence. First, the calculator works out how wide each panel needs to be after gathering. It divides your track width by the number of panels and multiplies by the fullness ratio. For a 60-inch track with two panels at 2 times fullness, each panel needs 60 inches of gathered fabric.

Next, it determines how many fabric widths each panel requires. If each panel needs 60 inches of gathered width and your fabric is 54 inches wide, that is two fabric widths per panel (you cannot use a partial width). Two panels at two widths each means four fabric widths total.

The cut drop for each width is your finished drop plus your combined hem allowance — typically 6 inches for a double-fold bottom hem and 6 inches for the heading, totalling 12 inches. If you are working with patterned fabric, the cut drop rounds up to the next full pattern repeat so all widths match when hung side by side. Our guide to understanding pattern repeat explains how this works for both standard and half-drop repeats.

Total fabric equals the number of widths multiplied by the cut drop, converted from inches to yards or metres. The calculator rounds up to the nearest ⅛ yard or 10 cm for purchase convenience.

Measuring Your Window

Good curtains start with good measurements. Getting these wrong means fabric that pools on the floor, stops short of the sill, or does not cover the window fully when drawn closed.

• Track or pole width: measure the full span of your curtain track or pole, from end to end — not the window opening itself. If the track extends beyond the window frame (for stack-back), include those extensions.
• Finished drop: measure from the top of the heading (where the curtain attaches to the track or rings) to where you want the bottom of the curtain to fall. For sill-length curtains, stop at the sill. For floor-length, measure to 1 cm above the floor. For a puddling effect, add 5 to 15 cm.
• Bay windows: measure each section of the bay separately. If your bay has a curved track, measure the full curved length. For three-panel bays, enter the total track width and set the panel count to three — the calculator divides fabric evenly.

Measure at least twice, and measure from the fitting rather than the window frame. A curtain pole sits above the frame, so the drop measurement starts from the pole rings, not the top of the window.

Pattern Repeats on Curtains

Patterned curtain fabric costs more to use than plain fabric because each drop must be cut at the same point in the pattern. This is what allows stripes, florals, or geometric designs to match across seams when multiple widths are joined.

A standard pattern repeat rounds the cut drop up to the next complete repeat. If your cut drop is 96 inches and the repeat is 12 inches, the drop stays at 96 (already a multiple). If the drop were 97 inches, it would jump to 108 (nine full repeats).

A half-drop repeat adds visual interest by offsetting alternating columns by half the vertical repeat. Calculating for a half-drop does not change the total yardage — the cut drop still rounds up to the next full repeat. The difference is in cutting layout: every other width is shifted by half the repeat distance, which affects how you align the fabric during sewing.

On an expensive fabric with a large repeat, the waste from pattern matching can add a full yard or more to your requirements. The roman blind fabric calculator handles the same repeat logic for roman blinds.

Where People Go Wrong

Curtain fabric mistakes are expensive. The quantities involved are larger than most sewing projects, so errors compound quickly.

• Measuring the window instead of the track. A 48-inch window with an 8-inch stack-back on each side has a 64-inch track. Measuring only the window means your curtains will not close fully.
• Underestimating fullness. Flat curtains (1 times fullness) look lifeless. Pencil pleat heading tape is designed for 2 to 2.5 times — cutting to less means the pleats will not form properly and the tape will be visible.
• Forgetting hem allowance. The cut drop must include both the heading and the bottom hem. A 6-inch double-fold bottom hem plus a 6-inch heading adds 12 inches to every width of fabric.
• Splitting a width between panels. Each panel is made from complete fabric widths. You cannot take leftover width from one panel and use it for another — the seam positions would be asymmetric. If you have excess width per panel, trim it during making.
• Not buying enough for matching. If you run short on patterned fabric and reorder, the new bolt may be from a different dye lot. Pattern placement can also shift between print runs. Buy everything from one bolt whenever possible.

If you are also making window treatments for other rooms, the fabric yardage calculator covers general fabric projects, and the yards-to-metres converter helps when your supplier quotes in a different unit system.