Curtain Fabric Calculator

🔧 Plan Your Curtains

What is a Curtain Fabric Calculator?

A curtain fabric calculator turns a window's measurements into the yardage you need to make curtains for it. You enter the track or pole width, the finished length you want them to hang, and a fullness ratio for the gather, and it works out how many widths of fabric to join and how much to buy in total.

The maths follows how curtains are actually made. The track width is multiplied by the fullness to get the gathered width, then divided by the fabric width to find how many widths must be sewn side by side. Each width is cut to the finished drop plus a header-and-hem allowance, and if the fabric has a pattern repeat, every cut is rounded up to a whole repeat so the design matches across the seams.

The result is the number of widths, the cut length of each, and the total yardage to buy for the whole window. Whether you're making crisp cotton curtains for a kitchen, heavy lined drapes for a living room, or sheer voiles for privacy, working out the fabric first means you buy the right amount and achieve the full, even gather that makes curtains look properly finished.

📖 How to Use the Curtain Fabric Calculator

1Measure the Track and Drop

Measure the width of the track or pole, not the window, since curtains run the full length of the track. Then decide the finished drop — how far down you want the curtains to hang, whether to the sill, below it, or to the floor.

Use a steel tape for accuracy and measure twice. The finished length is the visible drop you want; the calculator adds the heading and hem on top of it.

2Choose Your Fullness

Set the fullness ratio for the look and heading you want. A 2.0 ratio is the standard for pencil and pinch pleats and gives a generous gather; lighter curtains use 1.5, while luxurious drapes and sheers can go to 2.5 or 3.0.

Remember that more fullness means more fabric and a fuller, more draped result — match the ratio to the heading style and the richness you're after before you commit.

3Enter Fabric Width and Pattern Repeat

Tell the calculator the usable fabric width — furnishing fabric is often 54 inches — so it can work out how many widths to join. Then enter the vertical pattern repeat if your fabric is patterned, or zero for plain cloth.

Set the header-and-hem allowance too; 16 inches suits a standard heading and a generous double hem on most curtains, but increase it for deep hems or elaborate headings.

4Read and Buy Your Fabric

The calculator reports the number of fabric widths, the cut length of each, the total length, and the yardage to buy, rounded up to the nearest quarter yard. Buy that amount in a single cut from one dye lot.

Cut each width to the stated length, matching the pattern across the seams, then join the widths and divide them between the two curtains, keeping the design balanced across the pair.

💡 Practical Curtain Tips

Measure the track, not the window: Curtains span the full pole or track width, which is usually wider than the glass
Match the pattern across seams: Cut each width to a whole repeat so the design flows unbroken across joined widths
Buy one dye lot: Get the full yardage in a single cut so the colour matches across every width
Allow generous hems: A deep double hem hangs better and adds weight, so don't skimp on the allowance
Pick fullness for the look: 2.0 is a safe standard; go fuller for luxury, lighter for economy
Consider lining: Lined curtains hang better, block light, and insulate — remember to buy lining fabric too

🎯 Benefits of Calculating Curtain Fabric

🎯 Buy the Exact Amount

Working out widths and yardage before you shop means you buy precisely what the window needs from a single dye lot — no costly over-buying and no running short mid-make.

🌊 Get a Full, Even Gather

Applying your chosen fullness ratio guarantees the curtains have enough fabric to drape and gather properly, instead of hanging flat and stretched across the track.

🧩 Match Patterns Cleanly

By rounding each cut to a whole pattern repeat, the calculator ensures the design lines up across every seam for the seamless look of professionally made curtains.

📐 Allow for Headers and Hems

The built-in allowance means your finished curtains hang at exactly the drop you wanted, with proper headings and deep hems, not cut short by forgotten turnings.

🏠 Furnish Any Window

From a small kitchen window to a wide patio door, the same logic scales to any track width and drop, so you can dress every room with confidence.

💷 Save Over Bespoke

Made-to-measure curtains are expensive; calculating your own fabric and sewing them yourself delivers the same custom fit for a fraction of the cost.

❓ Frequently Asked Questions

What is curtain fullness and what ratio should I choose?

Fullness is how much wider the flat fabric is than the track or pole it hangs from, and it's what gives curtains their gathered, draped look instead of a flat, stretched panel. A fullness of 2.0 — twice the track width in fabric — is the common standard for pencil-pleat and pinch-pleat headings and gives a generous, even gather. Lighter, more economical curtains might use 1.5, while luxurious heavy drapes or sheer voiles can go to 2.5 or even 3.0 for a really lush wave. The heavier the fullness, the more fabric you buy, so choose the ratio to match the heading style and the look you're after before the calculator multiplies it out.

Why do I need to add allowance for the header and hem?

The finished length you want is the visible drop from the top of the curtain to the bottom, but the fabric has to be longer than that to form the heading at the top and the hem at the bottom. The heading takes a turning for the tape or pleats, and curtains traditionally have a deep double hem for weight and a quality hang. A combined allowance of around 16 inches covers a standard heading and a generous hem on most curtains, though you can increase it for very deep hems or elaborate headings. The calculator adds this allowance to your finished length before working out the cut length of each fabric width.

How does a pattern repeat affect how much fabric I need?

A pattern repeat is the vertical distance over which a printed or woven design repeats itself. When you join fabric widths side by side to make wide curtains, the pattern must line up across the seams, and that means cutting each length to a whole number of repeats rather than the bare minimum. The calculator rounds each cut length up to the next full repeat, which can add noticeable fabric on large-repeat designs but is essential for a professional finish where the motif flows unbroken across the whole curtain. For plain fabric, set the repeat to zero and no extra length is added.

Does the calculated yardage cover one curtain or a full pair?

The figure covers all the fabric needed for the window you've entered, gathered to your chosen fullness — which for most windows means a pair of curtains that meet in the middle. The calculation works from the total gathered width across the whole track, so it doesn't matter whether you split that into two curtains or hang a single one; the fabric quantity is the same. When you cut, you simply divide the total fabric widths between the two curtains as evenly as the design allows, keeping any pattern centred or balanced across the pair for a polished result.