How much fabric do you need for curtains? Enter your rod width, finished curtain length and fabric width to estimate full-width drops, cutting length, metres or yards to buy, and fabric cost. The calculator accounts for fullness, seams, hems and straight pattern repeats.
How to use the curtain fabric calculator
- Choose inches, feet, centimetres or metres. Enter the rod or track span and the finished fabric drop.
- Select one curtain or a pair of equal curtains. Enter the fullness required by your chosen heading and the number of identical windows.
- Enter the usable fabric width. Choose plain fabric or a straight pattern repeat. For a repeating design, enter the measured vertical repeat and decide whether to reserve one extra repeat for initial placement.
- Open the allowance section. Check both side hems, joining seams, the top, the bottom and any extra straightening length.
- Choose metres or yards for buying, enter the seller's increment and any extra reserve. Add an optional fabric price, then select Calculate curtain fabric.
The result shows how many full-width drops to cut, the cutting length of each drop and the combined order. A fabric width is a strip cut across the usable roll width. Several strips can be joined to make one curtain panel. A pair of curtains is two panels, not necessarily two fabric widths.
Use decimal numbers with a point or comma, without fractions or thousands separators. Enter 0.5 instead of 1/2. Unit changes convert the existing values. After changing a value, calculate again.
Which curtain measurements do I need?
Use the span of the installed or planned rod or track that the curtains need to cover. Decorative finials do not count as covered width. A curtain rod often extends beyond the glass, so the window opening alone can give too little fabric.
Finished drop means the final length of the fabric itself, from its top edge to the bottom hem. Rings, hooks, heading tape and eyelets can place that top edge at different heights. Decide where the fabric top will sit and whether the hem should clear the floor or pool on it. Enter that finished length before adding sewing allowances.
The additional covered-width field is for finished returns or extra centre overlap not already included in the measured span. The calculator applies fullness to this combined width. If your workroom treats returns or overlap differently, obtain its required covered width and allowances first. Do not add the same overlap twice.
What does curtain fullness mean?
Fullness compares the flat fabric width before gathering with the span it will cover. A ratio of 2 means 4 m of flat fabric for a 2 m span. A ratio of 1 gives a flat treatment without extra gathering. The suitable ratio depends on the heading system, fabric weight and the appearance you want.
The initial ratio of 2 is a planning input, not a rule for every curtain. Use the value specified for your heading tape or track system. This calculator does not place individual pleats, eyelets, hooks or wave carriers.
Rounding to whole fabric widths can provide more flat width than requested. The results show the available flat width after side hems and seams, plus the possible fullness if you keep all of it. You can trim the panel to your planned fullness following your sewing method. Buying fewer full-width drops is a different layout decision.
How curtain fabric is calculated
Covered span = rod or track width + additional covered width.
Required flat width per panel = covered span × fullness ÷ panels per window.
For n fabric widths in one panel, available flat width = n × usable fabric width − 2 × seam allowance × (n − 1) − 2 × side hem allowance.
The calculator chooses the smallest whole number n that provides the required flat width. The seam allowance is for one joined edge, so each join uses it twice. Side hems are deducted only at the two outer edges of the finished panel.
Base cut drop = finished drop + top allowance + bottom allowance + straightening allowance.
For plain fabric, this is the cut length per full-width strip. For a straight repeat, cut length = the base cut drop rounded up to a whole number of vertical repeats. The optional first-repeat reserve is added once to the combined continuous fabric length, not once to every strip.
Total widths = widths per panel × panels per window × identical windows. Multiply this count by the cut length and add the initial repeat reserve. Apply any additional reserve percentage to that result, then round the combined purchase up to the retailer's selling increment.
Example: a pair of curtains for a 2 m rod
Use a 200 cm rod, 240 cm finished drop, two equal panels and fullness of 2. The fabric has 140 cm usable width. Allow 4 cm total for each outer side hem and 1.5 cm on each joined edge. These are example inputs, not a specification for your sewing method.
Each panel needs 200 cm of flat width. One fabric width provides 140 − 8 = 132 cm after side hems. Two widths provide 280 − 3 − 8 = 269 cm after one seam and the side hems. The whole-width method therefore allocates two widths to each panel, four widths in total.
With 10 cm at the top, 20 cm at the bottom and no extra straightening, the base cut drop is 240 + 10 + 20 = 270 cm. Plain fabric needs 4 × 270 = 1080 cm, or 10.8 m, before any extra reserve.
For a 60 cm straight repeat, round each cut drop up to 300 cm. Four drops use 12 m. Reserving one further repeat for the initial pattern position adds 0.6 m, giving 12.6 m. A seller using 0.1 m increments can supply 12.6 m. At an illustrative EUR 20 per metre, face fabric costs EUR 252.
Keeping all 269 cm of flat width in each panel would give 2.69 times fullness across the 200 cm rod. If your heading needs exactly twice fullness, the panel widths must be trimmed appropriately. Load example fills the patterned version of these inputs.
Does this find the smallest possible fabric order?
No. It uses whole widths for each equal panel and keeps the fabric running vertically. A workroom may use half widths, share a split width between a pair, or choose a different roll width to reduce the order. Those layouts can change seam positions and pattern placement.
Use this result as a transparent whole-width shopping estimate. It is not a nesting optimizer or a complete sewing pattern. Do not assume the rounded excess can always supply another panel.
How do pattern repeats affect curtain fabric?
A straight repeat returns to the same motif position after a fixed vertical distance. Rounding each cut drop to a whole repeat allows consecutive drops to begin at the same vertical pattern phase. The optional extra repeat gives room to choose the starting motif when the supplier's cut begins elsewhere in the design.
Check the actual repeat and usable matching width before buying and again before cutting. Vertical rounding does not calculate horizontal pattern trimming, motif centring or the placement of a specific flower at every leading edge. Use a usable width that already accounts for the pattern match across seams.
Half-drop or offset matches, border fabrics, unusual repeats and railroaded layouts require a separate cutting plan. Selecting that option produces a message instead of a misleading quantity. Do not treat a half-drop design as a straight match.
How much should I allow for double hems and seams?
Enter the total fabric consumed by both folds. For example, a bottom hem folded by 8 cm twice uses a 16 cm allowance. A 2 cm fold repeated twice at an outer side uses 4 cm for that edge. These examples explain the inputs; choose the actual amounts for your project.
At a vertical joining seam, an allowance of 1.5 cm on each edge consumes 3 cm in total. With three strips in one panel there are two joining seams. The outer side hems are still counted only twice for the whole panel.
Any extra straightening allowance is added to each cut drop before pattern rounding. If pattern rounding already leaves enough material to straighten the cut, avoid counting the same margin twice.
Are lining, shrinkage and separate fabric cuts included?
The result covers the face fabric only. Lining and interlining may have different usable widths, finished lengths and hemming methods, so calculate them from their own workroom cutting specifications. Do not automatically order the same quantity as the face fabric.
Shrinkage is not calculated. Use the fabric supplier's care instructions and confirmed dimensions after any required preparation. A general spare percentage does not ensure that every individual strip remains wide or long enough after shrinkage.
The first-repeat allowance assumes one continuous length of matching fabric for all identical windows. Separate cuts or rolls may each need a fresh pattern-placement allowance. Different windows, fabric widths, colours or repeats should be calculated separately. Do not subtract unrelated short remnants as if they formed one continuous cut.
What is included in the price?
Cost equals the rounded purchase length multiplied by the price per selected metre or yard. One yard is exactly 0.9144 m. The buying-unit selector converts an entered price when you change between these units, while a currency change does not apply an exchange rate.
The price excludes lining, interlining, heading tape, weights, hooks, rods, sewing, installation, delivery and taxes not included in your entered fabric price. Check the supplier's minimum order and increment. This calculator rounds by the increment but does not add a separate minimum order.
Check the fabric and heading instructions
The BIID guide to window surveying and fabric calculations discusses finished drop, heading choices and fabric repeats. Sew Helpful's curtain fabric guide explains straight-repeat cutting and initial motif placement. Sailrite's curtain planning notes also distinguish fabric widths from finished panels. Their construction methods and default allowances can differ from this tool, so follow the method chosen for your actual curtains.
For other room updates, try our window film calculator, paint calculator and baseboard calculator. The generated photo illustrates a curtain project and does not specify exact dimensions or a sewing method.
