Curtain & Blind Sizing Calculator
Calculate curtain fabric yardage, fullness ratios, finished drop length, rod stack-back width, and inside/outside mount window blind dimensions.
Window & Curtain Specifications
Curtain Sizing & Fabric Requirement
✂️ Hem Allowance & Hardware Advice
Calculation includes a standard 8-inch double-fold bottom hem and 4-inch header allowance (12 inches total cut length per drop). Mounting your curtain rod 6 inches above the frame and extending 8 inches past the casing makes your window appear substantially larger and allows maximum daylight into the room when curtains are stacked open.
About this tool
How to use it
- Choose your window treatment type (Hanging Curtains or Window Blinds) and select your window dimensions or pre-set template.
- For curtains, specify your desired drop style (sill, apron, floor, or puddle), fullness ratio (1.5x to 2.5x), and rod overhang extension.
- For blinds, choose between inside mount (casing recess) or outside mount (wall trim overlap).
- Click 'Calculate Sizing & Yardage' to retrieve exact fabric yardage cuts, finished drop lengths, and manufacturer ordering dimensions.
Why it matters
Ordering custom curtains or window blinds without factoring in fullness gather, hem allowances, and manufacturer deductions leads to flat, skimpy drapes or blinds that scrape casing and leak edge light. Accurate calculations ensure professional interior-designer results on the first order.
When to use it
Use this calculator before purchasing fabric by the yard at upholstery stores, ordering custom roman shades or roller blinds online, or installing curtain rod hardware during home decorating.
Good to know
Curtain calculations automatically add a 12-inch cut allowance per drop (8-inch double bottom hem + 4-inch top header). Blinds calculations apply standard industry deductions (3/8" width reduction for inside mount; 2" perimeter overlap for outside mount).
Common questions
What is curtain fullness ratio and why does it matter?
Fullness ratio represents the total width of the fabric before gathering relative to the width of the curtain rod. A 2.0x fullness (standard) means 100 inches of rod requires 200 inches of fabric width. Without proper fullness, closed curtains hang flat like a sheet instead of displaying deep, elegant fabric pleats.
How high above the window should I mount the curtain rod?
Interior designers recommend mounting the curtain rod 4 to 8 inches above the top of the window casing (or halfway between the casing and ceiling moulding). High rod placement draws the eye upward, giving the illusion of higher ceilings and larger windows.
What is rod stack-back?
Stack-back is the width occupied by the curtains when fully pulled open. Extending the curtain rod 6 to 10 inches beyond the window casing on each side allows the open drapery panels to rest against the wall rather than blocking the glass and natural daylight.
What is the difference between inside and outside mount blinds?
Inside mount blinds fit within the recessed window casing, providing a sleek, built-in aesthetic. Outside mount blinds mount on the wall or trim outside the opening, which is necessary when window casings lack sufficient depth (under 2.5 inches) or to completely cover trim imperfections.
How do I measure for inside-mount window blinds?
Measure width across three locations: top, middle, and bottom of the casing, and use the narrowest measurement. Measure height from top casing to sill at three spots and use the longest measurement. Do not make deductions yourself; manufacturers deduct approximately 3/8" for clearance.