What size curtains do I need for my window?

You need two numbers: width and length. For width, size the combined panels to at least twice your rod width, and run the rod about 8 inches past each side of the glass. For length, measure from where the rod sits down to where you want the hem, then round up to a standard panel length. The calculator does both from your exact window, so you buy the right off-the-shelf panels instead of guessing.

How wide should curtains be for the window?

Aim for total panel width equal to about two times the rod width — that is the standard gather that makes closed curtains look full rather than flat and stretched. Since the rod itself runs roughly 16 inches wider than the window (8 inches each side), a 36-inch window on a 52-inch rod wants about 104 inches of fabric across, or two 52-inch panels. Drop to 1.5x only for sheers; go to 2.5-3x for a luxe, heavily gathered look.

How long should curtains be?

It depends on the look. Floor length — panels that just kiss the floor with about a half-inch gap — is the most common, tailored choice. Sill length ends right at the windowsill (good for kitchens). Apron length falls about 4 inches below the sill. Puddle length pools a few inches of fabric on the floor for a soft, formal feel. Measure from the rod down to the target hem, then round up to the nearest stock length and hem down.

What are standard curtain panel lengths?

Ready-made panels come in a handful of stock drops: 63, 84, 95, 108, and 120 inches. 63-inch panels suit short or sill-height windows, 84 inches is the everyday standard, and 95, 108, and 120 inches handle taller windows or high-mounted rods. The calculator snaps your finished drop up to the nearest of these, because shortening a panel by hemming is easy while adding length is not. A drop over 120 inches means a custom order.

How high should I hang a curtain rod?

Mount the rod 6 to 12 inches above the window frame — higher draws the eye up and makes both the window and the ceiling feel taller. For ceilings around 8 feet, 6 inches above the frame is a safe start; for 9-foot-plus ceilings you can go higher or even mount near the ceiling line. Also extend the rod about 8 inches past each side of the glass so open panels stack off the window and let in full light.

How many curtain panels do I need?

Most windows use two panels — one drawn to each side — because a pair frames the window and each panel only has to cover half the opening. A single panel works for narrow windows or a one-sided pull. Very wide windows and sliding doors often need three or four panels to keep each one full when closed. Whatever the count, the total fabric width across all panels should still hit about twice the rod width.

How much fabric do I need to make curtains?

For each panel, take the finished drop, add about 8 inches for the top header and bottom hem, then divide by 36 to get yards. Multiply by the number of panels. An 84-inch drop across two panels works out to roughly (84 + 8) / 36 x 2, about 5.2 yards. Add extra for patterned fabric so the repeat lines up, and remember wide windows may need two or three fabric widths seamed together per panel to reach the fullness target.

How accurate is this curtain size calculator?

It follows standard drapery conventions — rods 8 inches past each side, 2x fullness for a proper gather, and drops snapped up to real 63/84/95/108/120-inch stock lengths — so it gets you to the right purchase in one step. It sizes single flat panels; for pinch-pleat, grommet spacing, or very wide sliders you may seam widths or adjust the panel count. Treat the fabric yardage as a starting point and add for pattern repeats and generous hems.

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Curtain Size Calculator — Panel Width, Length & Fabric (2026)

Enter your window size, drop style, and fullness — get the curtain panel width, finished length, rod width, and fabric yardage, snapped to standard 63/84/95/108/120-inch stock lengths so you can buy off the shelf.

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AI insight included

Window width

Width of the window opening (frame to frame), in inches.

Window height

Height of the window opening (frame to frame), in inches.

Sill height

Floor to the bottom of the window (the window sill), in inches.

Rod height above window

How far above the window top the rod is mounted (6-12 in is typical — higher makes the window look taller).

Drop style

Where the hem lands. Floor-length is the most common, tailored look.

Fullness

Fabric width as a multiple of the rod width. 2x is the standard gather; below 2x looks flat.

Number of panels

How many curtain panels. Panels almost always hang in pairs (2 per window).

Reviewed by CalcBold Editorial · Sources: standard drapery / window-treatment sizing conventions (rod extension 8 in per side, 2x fullness gather, standard 63/84/95/108/120-inch panel drops)Last verified July 23, 2026Methodology

For a standard 36-inch window, floor-length panels are the safe default: hang the rod 6–12 inches above the frame and 8 inches wider on each side, then buy panels roughly 2× the rod width so they gather full. Enter your window size and fullness above for the exact panel width, length, and fabric yardage.

What size curtains do I need? — the short answer

Buy panels whose combined width is at least 2× your rod width(and the rod runs 8 inches past each side of the glass), then pick the finished length for your drop style. Rough guide: two 84-inch panels suit an average window with a rod about 5–6 feet up, 95 or 108-inch panels handle taller windows, and puddled looks size up one stock length. The calculator above turns your exact window into the right off-the-shelf panel width and length.

What This Calculator Does

Enter your window width and height, the sill and rod-mount heights, your drop style, fullness, and panel count — get the flat panel width to buy, the finished drop snapped to a standard 63 / 84 / 95 / 108 / 120-inch stock length, the rod width, and the fabric yardage if you are sewing your own. It follows standard drapery conventions so the recommendation maps to panels you can actually buy off the shelf.

The Math / Formulas Used

Fullnessis the dial that makes or breaks the look: at 1.5× the rod width panels look flat and skimpy, 2×is the standard gather, and 2.5–3× is the full, luxe drape. The finished drop is measured from where the rod sits off the floor down to where the hem should land, then snapped upto the nearest stock length so you can hem down to the exact height — shortening a panel is easy, adding length is not.

The four drop styles

Sill lengthends right at the windowsill — tidy for kitchens and behind a sink. Apron falls about 4 inches below the sill, a practical mid-length. Floor length just clears the floor (about half an inch of gap) and is the most common, tailored look. Puddlepools a few inches of extra fabric on the floor for a soft, formal feel — size up one stock length and expect to steam the pool into place.

How to Use This Calculator

Measure the window opening frame-to-frame for width and height, then the floor-to-sill height and how far above the window you plan to mount the rod (6–12 inches makes the window look taller). Choose your drop style, fullness, and how many panels, then read the panel width and stock length to buy. When you are done, the buying and sizing guides cover the rest of the room, from curtain drop to bedding sizes.

Frequently Asked Questions

The most common questions we get about this calculator — each answer is kept under 60 words so you can scan.

What size curtains do I need for my window?
You need two numbers: width and length. For width, size the combined panels to at least twice your rod width, and run the rod about 8 inches past each side of the glass. For length, measure from where the rod sits down to where you want the hem, then round up to a standard panel length. The calculator does both from your exact window, so you buy the right off-the-shelf panels instead of guessing.
How wide should curtains be for the window?
Aim for total panel width equal to about two times the rod width — that is the standard gather that makes closed curtains look full rather than flat and stretched. Since the rod itself runs roughly 16 inches wider than the window (8 inches each side), a 36-inch window on a 52-inch rod wants about 104 inches of fabric across, or two 52-inch panels. Drop to 1.5x only for sheers; go to 2.5-3x for a luxe, heavily gathered look.
How long should curtains be?
It depends on the look. Floor length — panels that just kiss the floor with about a half-inch gap — is the most common, tailored choice. Sill length ends right at the windowsill (good for kitchens). Apron length falls about 4 inches below the sill. Puddle length pools a few inches of fabric on the floor for a soft, formal feel. Measure from the rod down to the target hem, then round up to the nearest stock length and hem down.
What are standard curtain panel lengths?
Ready-made panels come in a handful of stock drops: 63, 84, 95, 108, and 120 inches. 63-inch panels suit short or sill-height windows, 84 inches is the everyday standard, and 95, 108, and 120 inches handle taller windows or high-mounted rods. The calculator snaps your finished drop up to the nearest of these, because shortening a panel by hemming is easy while adding length is not. A drop over 120 inches means a custom order.
How high should I hang a curtain rod?
Mount the rod 6 to 12 inches above the window frame — higher draws the eye up and makes both the window and the ceiling feel taller. For ceilings around 8 feet, 6 inches above the frame is a safe start; for 9-foot-plus ceilings you can go higher or even mount near the ceiling line. Also extend the rod about 8 inches past each side of the glass so open panels stack off the window and let in full light.
How many curtain panels do I need?
Most windows use two panels — one drawn to each side — because a pair frames the window and each panel only has to cover half the opening. A single panel works for narrow windows or a one-sided pull. Very wide windows and sliding doors often need three or four panels to keep each one full when closed. Whatever the count, the total fabric width across all panels should still hit about twice the rod width.
How much fabric do I need to make curtains?
For each panel, take the finished drop, add about 8 inches for the top header and bottom hem, then divide by 36 to get yards. Multiply by the number of panels. An 84-inch drop across two panels works out to roughly (84 + 8) / 36 x 2, about 5.2 yards. Add extra for patterned fabric so the repeat lines up, and remember wide windows may need two or three fabric widths seamed together per panel to reach the fullness target.
How accurate is this curtain size calculator?
It follows standard drapery conventions — rods 8 inches past each side, 2x fullness for a proper gather, and drops snapped up to real 63/84/95/108/120-inch stock lengths — so it gets you to the right purchase in one step. It sizes single flat panels; for pinch-pleat, grommet spacing, or very wide sliders you may seam widths or adjust the panel count. Treat the fabric yardage as a starting point and add for pattern repeats and generous hems.