How Much Fabric Do You Need for Curtains?
Use this curtain fabric calculator to turn pole or track width, finished drop, fullness and fabric width into the number of fabric drops and total yardage. You can also include returns, pair overlap, side hems, joined-width seam allowance, top and bottom allowances, straight or half-drop pattern repeat, lining and extra fabric for cutting mistakes.
The result shows the full cut length of every drop, how many fabric widths are required, the flat curtain width created by those drops, pattern-matching allowance, optional lining yardage and a recommended purchase quantity.
Curtain Fullness Starting Points
Fullness is the ratio between the flat fabric width and the space the finished curtains cover. Heading hardware and the look you want can change the ideal ratio, so the calculator keeps fullness editable even when you choose a heading preset.
| Heading style | Starting fullness | Calculator top allowance |
|---|---|---|
| Rod pocket | 2× | 6 in |
| Grommet / eyelet | 1.8× | 4 in |
| Pinch pleat | 2.5× | 4 in |
| Pencil pleat | 2× | 4 in |
| Ripplefold / wave | 2× | 4 in |
| Tab top | 1.5× | 6 in |
These are editable starting values, not fixed rules. Check your heading tape, track, grommet system or workroom specification before cutting.
Curtain Fabric Formula
The width calculation starts with the area the curtains need to cover:
Coverage width = pole or track width + both returns + center overlap for a pair
Required flat width = coverage width × fullness
The calculator then tests whole fabric widths until the usable finished width is large enough. It subtracts the outer side hems and the seam allowance consumed where multiple fabric widths are joined.
For a pair that needs an odd number of full fabric widths, the cutting plan can split one full drop lengthwise. For example, five full drops can become two curtains using 2.5 fabric widths each, with the half-widths placed at the outside edges.
How to Calculate the Cut Length of Each Curtain Drop
The unpatterned cut length is:
Cut length = finished drop + top allowance + bottom hem allowance + extra drop or puddle
The bottom hem field is the total fabric consumed by the hem. If your construction uses a double 4-inch hem, enter 8 inches. If your heading needs more or less cloth than the preset, edit the top allowance directly.
Pattern Repeat for Curtains
Pattern matching is one of the main reasons curtain yardage can rise quickly. With a straight repeat, every drop is rounded upward to a whole vertical repeat so motifs can line up across joined widths and across a pair.
Repeat-adjusted drop = next whole repeat at or above the basic cut length
For a half-drop repeat, alternate fabric widths are offset. The calculator rounds each drop to the repeat and adds one additional full vertical repeat to the order for each window when more than one width is required. Very large motifs may still need extra cloth if you want a specific flower, medallion or stripe positioned at the top or center of the curtain.
Straight Repeat vs. Half-Drop Repeat
| Pattern type | How this calculator plans it |
|---|---|
| Plain / no repeat | Uses the basic cut length with no repeat rounding. |
| Straight repeat | Rounds every cut drop up to a whole vertical repeat. |
| Half-drop repeat | Rounds every cut drop and adds one additional full repeat per window for the alternating offset. |
How Many Fabric Widths Do You Need?
A curtain that needs more flat width than one fabric width must be seamed. The calculator does not simply divide by the bolt width and stop. It also accounts for the fabric consumed by the outer side hems and by joined-width seam allowances.
For a pair, an odd number of full widths can be shared evenly by splitting one width lengthwise. This is why a result may show 2.5 widths per curtain even though you still buy and cut five full drops.
Returns and Center Overlap
A return is the distance the curtain wraps from the front of the rod or track toward the wall. Add the return at each side when the curtain needs to cover that space. For a pair, center overlap adds fabric where the two curtains meet. Both values increase the coverage width before fullness is applied.
Curtain Lining Yardage
Turn on Include lining to calculate a separate lining purchase. Enter the usable lining width and the total top-and-bottom allowance for the lining construction. The calculator uses the same finished coverage and fullness as the face fabric, then finds the number of lining widths required independently.
Lining is not rounded to the face-fabric pattern repeat. If your lining has its own repeat or special orientation, calculate it separately using its actual cutting requirements.
Worked Example: 72-Inch Track, 84-Inch Drop
Suppose you are making a pair of curtains for a 72-inch track with a finished 84-inch drop, 3-inch returns at both sides, 2 inches of center overlap, 2× fullness and 54-inch usable fabric. With 1.5-inch outer side hems and 1/2-inch joined-width seam allowance, the calculator determines the whole number of fabric drops needed to provide enough finished flat width.
With the default 4-inch top allowance, 8-inch bottom hem allowance and no pattern repeat, each drop is cut 96 inches long. If you add an 18-inch vertical repeat, every drop is rounded upward to the next whole repeat before the total yardage is calculated.
Measure the Pole or Track, Not Only the Glass
The fabric must cover the installed treatment span. Measure the rod or track width that the curtains actually travel across rather than only the visible glass. Add returns and overlap separately in the calculator instead of hiding them inside the window measurement.
Curtain Fabric Calculator FAQ
How do I calculate how much fabric I need for curtains?
Multiply the coverage width by the desired fullness, then determine how many usable fabric widths are needed after side hems and joined-width seams. Multiply the number of cut widths by the repeat-adjusted cut length and add any shopping allowance.
How much fullness should curtains have?
Many curtain styles begin around 1.5× to 2.5× fullness, but the correct number depends on the heading system, fabric weight and desired appearance. The calculator presets are editable so you can use the specification for your hardware or project.
How do I calculate fabric for a pair of curtains?
Enter the full pole or track width and choose Pair. The calculator treats the entered fullness as the total fullness across both curtains, includes both outer side hems and can split one full fabric width lengthwise when an odd number of widths must be shared between the pair.
What does 2× curtain fullness mean?
Two-times fullness means the flat finished curtain width is twice the coverage width. A 72-inch coverage width therefore needs about 144 inches of finished flat curtain width before accounting for side hems and joining losses.
How do I allow for a curtain pattern repeat?
Enter the vertical repeat and choose Straight or Half-drop. The calculator rounds the basic cut length upward to a whole repeat. Half-drop also receives an extra full repeat per window when multiple widths are needed.
Do side hems affect the number of fabric widths?
They can. Side hems consume part of the outside edges, so a width calculation that is very close to the limit may require another fabric width after hem and joining losses are included.
Can I calculate curtain lining too?
Yes. Turn on lining, enter its usable fabric width and the total top-and-bottom lining allowance. The result shows the lining purchase separately from the face fabric.
Should I buy extra curtain fabric?
A small extra allowance helps with flaws, trimming, a miscut or future repairs. The calculator defaults to 5% after whole-width and repeat rounding, and you can increase or remove that percentage.
Related Fabric Tools
For rectangular pieces and general projects, use the upcoming Fabric Yardage Calculator. For seating projects, use the Cushion Fabric Calculator or Upholstery Fabric Calculator.