State what your measurements describe
Before using a tape, name the room and label every window. Decide whether you are recording the visible opening, an existing track or a proposed wall coverage area. If the fitting method is undecided, say so. These are preliminary observations for discussion and estimation, not cutting dimensions. Manufacturer deductions, overlap, brackets and other fitting details must be resolved for the selected product by the responsible supplier or installer.
Record widths and heights separately
For an accessible opening, write widths at the top, middle and bottom, and heights on the left and right. Add the centre height if it helps describe a visibly uneven opening. Keep every reading with its position rather than selecting one or calculating an average. Record units on each sketch. Recheck a surprising result before sending it, and mark any value you could only estimate as approximate.
Show depth, movement and obstructions
Photograph the complete window and nearby wall, then show handles, sills, radiators, furniture and ceiling recesses. Describe how the sash opens and where an existing track starts and ends. For curtains, identify the finished floor level if it already exists. For screens, show the frame and opening arrangement without dismantling it. Do not lean outside or climb on furniture to obtain an inaccessible dimension; request a site visit instead.
Work through a conditional area example
Suppose an enquiry asks for two equal rectangular coverage areas, each 2 metres wide and 2.5 metres high. Step one: confirm that both rectangles use those dimensions. Step two: calculate one rectangle, 2 × 2.5 = 5 m². Step three: multiply by two, giving 2 × 2.5 × 2 = 10 m². This is the combined geometric coverage area in this example, not the area of curtain fabric to buy.
Keep fabric quantity separate from geometry
A curtain's fullness factor describes a separate design choice, while headings, hems, seams, pattern repeat and available fabric width also affect cutting plans. Two panels or two windows must be identified clearly so the count is not applied twice. Do not treat the example as an order calculation. Ask the supplier which dimensions and quantity their quotation uses, and have fabric requirements calculated after the construction is agreed.
Send a record that can be checked
Provide one numbered sketch per window, the original readings, units, photographs, proposed product and any uncertain access or floor information. Match each image to its window reference. Ask the installer to confirm final mounting and finished dimensions before cutting, sewing or ordering mechanisms. Keep the approved revision so earlier preliminary notes cannot be mistaken for the production specification. If the room changes during renovation, request a fresh check.