Identify where the measurement begins
A curtain can be several centimetres wrong even when the tape reading is accurate. The problem may be the starting point: top of pole, eyelet position, track glider or hook location. Choose the heading and hardware before deciding the drop, and obtain the seller's exact measurement convention.
Fabric tabs loop over the green pole, making the attachment distinct from the curtain’s hanging cloth. Identify your actual heading and hardware before asking the seller which named point starts its drop measurement. Use that specified convention rather than choosing an edge by appearance; this example shows the attachment but supplies no drop reading or universal starting rule.
Photo & usage
Wilfredor · CC BY-SA 4.0 · Source. Display copies resized and encoded as WebP; no instructional details were fabricated or removed.
Keep finished drop separate from raw cut length. A maker may add its own heading and hem allowances, while a home-sewn project needs a construction plan. Do not add an allowance to a made-to-measure order unless the maker specifically requests it.
Use the installed hardware where the service requires it. If the rail is only proposed, record a provisional measurement and the dimension that must be confirmed later. A planned mounting height can change when suitable fixings, trim or ceiling features are assessed.
Choose the intended lower edge
Decide whether the curtain will finish above a sill, below it or near the floor. Check window handles, heating equipment, furniture and the way the room is cleaned. Use equipment instructions for required clearances instead of borrowing a decorative gap from a photograph.
Consider how the curtain moves during ordinary use. A hem that drags across a working route may be impractical even if the appearance is intentional. Ask the household members who open and close it to consider the proposed finish.
IKEA's measuring guidance prompts users to account for sills, radiators and furniture. Its product-system advice does not determine the right finish for every room. John Lewis's buying guide distinguishes service and heading choices, so use the actual order route's instructions when translating the chosen finish into a number.
Measure more than one vertical position
Take readings at the left, centre and right of the relevant span from the same defined hanging reference. Record the finished floor or sill level at each position. Do not assume that a level-looking rail and a visually straight floor are perfectly parallel.
Use safe access and a suitable measuring tool. If the hanging point cannot be reached safely, obtain appropriate help rather than balancing on furniture. A second person can assist with reading and keeping the reference consistent from the floor.
Recheck a surprising difference before choosing a length. A changed hook setting, tape angle or different floor finish can create an apparent slope. Mark the cause as unknown if it remains uncertain, and give the maker all the readings instead of averaging them without explanation.
Calculate a finish above an uneven floor
This illustrative example measures from the agreed hanging point to the floor: 244 cm on the left, 243 cm in the centre and 242 cm on the right. The household chooses a 1 cm minimum floor clearance, subject to its curtain maker's guidance.
A 241 cm finished drop would leave clearances of 3 cm, 2 cm and 1 cm respectively. A 243 cm drop would clear the left by 1 cm, meet the centre floor and extend 1 cm beyond the right reading. The shortest vertical distance is therefore the controlling observation for the chosen no-contact aim.
These invented figures do not establish the best visual treatment. A maker might propose another construction or an intentionally shaped solution. Send the three readings and the desired finish, and ask which order measurement its service requires. Do not silently substitute the arithmetic average of 243 cm.
Record heading adjustment without using it as a rescue plan
Some headings permit limited hook-position adjustment, while others have a fixed relationship to the hardware. Ask the seller what adjustment is designed into the actual curtain and how it affects coverage above the track.
Do not order an uncertain length on the assumption that hooks can compensate for any error. Adjustment may alter the top appearance, glider movement or available range. Keep it as a documented product feature, not an undocumented tolerance.
For multiple curtains in one room, use consistent references and note any different rail heights. Matching nominal drops may not produce matching lower edges where hardware or floors differ. The survey should explain those conditions before a maker commits fabric.
Check care and construction before hemming
Ask the manufacturer or maker how the fabric should be prepared and whether the finished product has relevant settling or care guidance. Do not assume every textile should be prewashed or hung for the same period. Linings and face fabrics can have different requirements.
Keep a home alteration reversible until fit is checked where the construction allows. Follow the product's hemming instructions and test the intended method on suitable spare material if available. An adhesive hem treatment is not automatically suitable for every fabric or lining.
If the curtain has a pattern, confirm the visual placement before shortening. Removing length can change where a motif meets the floor or sill. Width, heading and pattern decisions should be stable before an irreversible cut is made.
Submit a drop record the maker can interpret
Write the room, window identifier, hardware, heading, reference point, three readings and intended finish. State whether the submitted figure is finished drop or the maker's requested measurement. Keep a copy of the exact order.
Ask the supplier to resolve any ambiguous instruction before payment or cutting. If its form accepts only one number, explain the uneven readings and obtain its recommendation. A short written clarification is more useful than assuming the order system accounts for a condition it has never been told about.
For ready-made curtains, compare available drops with the alteration plan and return terms. Inspect the product before changing it. A curtain shortened to fit may no longer be returnable under the seller's terms, so identity and width checks belong ahead of alteration.
Check the full span in ordinary use
After hanging according to instructions, inspect the hem along the whole span with the curtains open and closed. Check that it does not catch on furniture or interfere with equipment. Operate windows where appropriate and observe actual clearance.
If the result differs from the plan, remeasure the hanging point and hook setting before cutting again. Document the discrepancy and consult the maker where needed. A second alteration based on the same mistaken reference can compound the error.
The length decision is complete when the intended finish works across the measured span and the order or alteration record explains the reference used. One attractive view from the doorway is not enough to confirm a consistent drop.
Compare neighbouring curtains from a shared reference
For several windows, label each measurement sheet and photograph. Record whether the rails share a level or follow different ceiling and trim conditions. Do not copy one window's drop to another because their frames appear identical.
Stand back and compare the intended lower edges in the room. A maker may need to reconcile uneven floors with a visually aligned finish, and that choice should be discussed before cutting. Keep the functional requirement, such as no floor contact, separate from the visual preference for matching hems.
If a new floor covering is planned, delay the final floor-length order measurement until the relevant finished level is known or obtain the maker's approved method. An existing bare-floor reading can become obsolete when the project adds material beneath the curtain.
THE REFERENCE FILE
Sources & scope
Documentation reviewed 1 Nov 2026. Examples are illustrative; this article does not claim hands-on product testing. Follow the instructions for your actual material, model and location.
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