Your starting point
Measure the installed pole or track and the required finished drop, using the exact attachment point for your heading style. Then calculate fabric fullness from the product’s instructions. A window-opening measurement alone is not enough to order curtains.
Decide the job of the window treatment
List the jobs separately: privacy, glare control, room darkening, insulation, or simply softening a hard edge. A sheer panel may suit daylight filtering but usually needs another solution for nighttime privacy. Blackout fabric can still leak light around the sides and top.
Look at the window open, closed, and with nearby furniture in use. Note radiators, heaters, vents, handles, and door swings. The appropriate product clearances take priority over a floor-length styling preference.
Where children live or visit, choose cordless window coverings and follow the CPSC guidance. Keep furniture away from accessible cords and do not treat decorative tiebacks as a substitute for a safe product.
Measure the support, not just the opening
For an existing pole, measure the usable span where the curtains can travel, excluding decorative finials. For a track, follow the supplier’s measuring instructions, including returns or overlaps if applicable. Write down the heading type: eyelet, tab, hook, ring, or another system.
When installing a new support, decide where the curtains stack when open. Extending beyond the opening can expose more glass, but the wall space and fixing positions must allow it. Check the wall construction and the support’s load rating.
In a rental, confirm permitted changes and retain the original fittings. A tension rod is not suitable for every opening or curtain weight.
Calculate the total fabric width
Fullness is the total flat curtain width divided by the usable support width. For example, a 200 cm support with a chosen fullness of 2 needs 400 cm of total flat panel width. Two 200 cm panels provide that amount before any product-specific differences.
A fullness around 1.5–2.5 is a common styling range, but the heading and fabric determine the appropriate choice. Follow the supplier’s recommendation for the actual item. Check whether a listing’s width refers to one panel or the pair; confusing the two can halve the fabric you receive.
Do not use fullness to compensate for an incorrectly measured support. Establish the span first, then choose the amount of fabric.
Measure the drop from the correct point
Measure from the point where the finished curtain actually hangs: this differs among eyelets, rings, hooks, and tracks. Follow the product diagram. Check the drop in at least three positions if the floor or ceiling may be uneven.
Decide whether the hem ends at a sill, below it, or near the floor. Fabric pooling is a styling choice that adds cleaning and can interfere with movement. A practical near-floor finish often suits an everyday room better.
Account for washing or shrinkage according to the fabric instructions, and confirm whether alterations affect returns. Do not guess the allowance; ask the supplier when the product does not state it.
Order from a written specification
Record usable support width, total required panel width, panel count, finished drop, heading, lining, and color. Add any hooks, rings, brackets, or suitable fixings needed to make the system complete.
Order a fabric sample where possible and view it against the wall in daylight and at night. Hold it up to the window if light transmission matters. A small swatch will not demonstrate complete blackout performance, but it can reveal texture and color differences.
Before opening packaging or altering the panels, compare the received dimensions and heading with the order. Keep installation instructions for future removal or adjustment.
Your practical checklist
Tick these as you go. Choices are saved in this browser when storage is available.
Common questions
Should curtains touch the floor?
They can, but the best drop depends on cleaning, circulation, nearby heat sources, and the look you want. Avoid fabric interfering with movement or required clearances.
Does a pair width mean each panel or both?
Listings differ. Confirm whether the stated width applies to one panel or the entire pair before ordering.
Can I use the window width as curtain width?
Not by itself. The support usually spans a different width, and the panels need the fullness required by their heading and fabric.
Sources & editorial approach
- U.S. Consumer Product Safety Commission: Go Cordless — Window-covering cord hazards and choosing cordless coverings where children may be present.
Source links reviewed October 3, 2026. Advice and examples are our editorial synthesis; dimensions are starting points, not universal requirements. How we create our guides.