How to Measure Windows for Curtains

Accurate curtain measurements begin with the installation you want, not simply the size of the glass. Curtains need to cover the opening, form the intended folds and finish at the right height. Their measurements depend on the rod or track, the heading and the way the panels will open. A few careful decisions before measuring can prevent expensive alterations later.

This guide explains how to measure windows for curtains in a straightforward home installation. It also identifies when to pause and request professional help. Use it to prepare a clear enquiry, then follow the final measuring convention of the supplier making your curtains. Do not cut fabric or approve custom production from approximate measurements alone.

First decide what you are ordering

There are three different tasks that people often call measuring curtains: measuring an opening for new hardware, measuring for made-to-measure curtains on an agreed installation, and checking whether ready-made panels will fit. Each uses related information, but the numbers should not be treated as interchangeable.

For new hardware, you need the intended mounting position and span. For custom curtains, the maker may ask for the track or pole width and a specified drop, then calculate fabric and fullness. For ready-made curtains, you need to understand the supplied panel dimensions and whether the listing describes one panel or a pair.

Tell the supplier which task you are doing before sending measurements. If your existing hardware is unsuitable, measuring it precisely does not make it the right basis for a new installation. Read Curtain Rails vs Curtain Rods if the support system has not yet been chosen.

Gather the right information and tools

Use a suitable rigid or retractable measuring tape, a notebook or measurement sheet, and a way to take clear photographs. Record dimensions consistently in millimetres or centimetres and label the unit on every figure. Avoid mixing metres, centimetres and inches in an informal message with no explanation.

Measure safely from a stable position. Do not balance on furniture or overreach to reach high fittings. Where the installation is high, awkward or otherwise unsafe to access, arrange professional measurement. A photograph and approximate dimensions are useful for an initial discussion without taking unnecessary risks.

Give each opening a name, such as Living Room Window A. Photograph the whole opening, surrounding walls, ceiling area and any handles or furniture that may affect the curtain. This helps the maker interpret the measurements and prevents similar windows being confused.

Step 1: inspect the existing rod or track

If you plan to retain the support system, check whether it is appropriate for the proposed curtain heading and weight. Note loose fittings, sagging, damaged gliders or movement that already feels difficult. A new lined curtain or extra sheer layer may require a different arrangement from the old lightweight curtain.

Record whether the support is a pole with eyelets, a pole with rings or a track with gliders and hooks. Photograph the connection at the top of the curtain. The exact heading affects the drop reference and the way the curtain travels, so a general description of a standard curtain is not enough.

Do not assume that the old curtain dimensions are correct. The previous curtain may have been too narrow, too short or made for another installation. Use the actual agreed hardware and desired finish as the basis, keeping the old measurements only as a clearly labelled reference.

Step 2: agree the hardware position if it is new

Before final curtain sizing, decide where the rod or track will be mounted and how far it will extend. Consider the opening, surrounding wall space, ceiling, doors and the place where open curtains will gather. The intended support span may extend beyond the glass, but the appropriate amount depends on the room.

Avoid applying a fixed extra allowance to every window without checking obstructions. A corner, cabinet or wall light may limit extension on one side. Finials require their own space. A balcony door may need a particular stacking arrangement so the curtain does not obstruct passage.

Confirm the plan with the installer before producing curtains. Measuring from an imagined pole height and later fitting it somewhere else changes the required drop. Where possible, use an installed and approved support system for the final curtain measurement, or obtain a clearly agreed installation drawing.

Step 3: measure the usable width

For a straightforward existing pole, measure the usable span between its decorative ends rather than including the finials in the curtain coverage. For a track, record the usable track span according to the maker's instructions. Overlap arms, returns and special configurations may require separate information.

This basic distinction is also reflected in the Poles and Blinds measuring guidance, which distinguishes pole width from decorative finials. Treat that as a general reference and use your own supplier's instructions for the actual system, especially where the hardware is not a simple straight installation.

Write down what the number represents. For example, state usable pole width, not just width. If you have also measured the glass or wall opening, label those separately. Sending several unlabelled numbers creates a risk that the wrong measurement will be used for production.

Step 4: distinguish coverage from flat fabric width

The width being covered is not necessarily the width of fabric needed. Fullness is the extra flat fabric that forms folds when the curtain hangs. The appropriate amount depends on the heading, fabric and intended appearance. It should be agreed rather than assumed from a universal rule.

For illustration, a 2-metre track at twice fullness corresponds to approximately 4 metres of combined flat curtain width before construction allowances. This is a simple explanation of fullness, not a cutting plan or an instruction to buy four running metres of material. Fabric width, seams, hems and pattern matching still affect the actual requirement.

For made-to-measure work, ask whether the supplier wants the hardware span and will calculate fullness themselves. Do not multiply the width and then submit it as the track width. That can result in fullness being added twice. For ready-made panels, confirm whether the stated width applies to one panel or the complete set.

Step 5: identify the correct drop starting point

The drop is the vertical measurement from an agreed hanging reference to the intended curtain finish. A hooked curtain on rings, a track-hung curtain and an eyelet curtain do not necessarily share the same reference. Ask the maker to identify the exact point rather than relying on a vague instruction to measure from the top.

For an eyelet heading, some fabric sits above the eyelet opening. The maker needs to explain how that upper fabric is accounted for in their order measurement. For rings or gliders, the curtain attaches below or at a particular connection point. The visible top of the hardware may not be the relevant starting point.

Record the convention in words alongside the number. A clear note such as drop measured from the maker-specified hook point is more useful than height alone. If instructions from different suppliers conflict, do not combine them; follow the one responsible for producing the curtain.

Step 6: decide where the curtain should finish

Choose whether the curtain will finish above the floor, lightly touch it or end at another appropriate point. Consider cleaning, pets, furniture and how frequently people pass the opening. A long pooling finish can be a deliberate decorative choice, but it may be inconvenient beside a busy door.

Do not subtract an arbitrary clearance without agreeing the desired finish. Measure and record the distance to the floor or other reference, then state the intended clearance separately if that is how the maker requests it. This keeps the physical measurement distinct from the design adjustment.

For shorter curtains, check sills and obstructions carefully. The fabric should not interfere with doors or rest against equipment that requires clearance. Follow relevant product and equipment guidance rather than choosing the drop solely from the appearance of another room.

Step 7: check the drop in several positions

Measure at the left, centre and right of a straight installation. Floors, ceilings and fitted hardware are not always perfectly level. Report meaningful differences rather than hiding them by sending an average. The maker or installer can then advise how the finish should be handled.

Check that the tape is vertical and that you are using the same starting point each time. A measurement taken diagonally or from a different ring can create an apparent variation that is not actually in the room. Repeat uncertain readings before recording the final figures.

If the differences are significant, stop and clarify the installation. A sloping pole or uneven fixing may need attention before curtain production. Do not attempt to compensate for a hardware problem by guessing a new curtain length without discussing the cause.

Step 8: record obstacles and opening movement

Measure or photograph projecting handles, deep sills, furniture and doors near the curtain. Explain whether the window opens inward and whether the curtain needs to clear a balcony entrance. These details affect the mounting projection and where the fabric can gather.

For layered curtains, account for both the sheer and the main curtain. Each needs space to hang and move without constantly rubbing the other. Read the sheer curtain guide before deciding on a two-layer arrangement using existing shallow brackets.

If stronger light reduction is required, mention it before agreeing width and mounting position. The blackout curtain guide explains why edge coverage and the centre meeting point matter as well as the fabric itself.

A sample measurement record

This is a template, not an order specification for your home. Its purpose is to show how labels prevent ambiguity. Keep approximate enquiry measurements separate from final approved measurements, and record the date and person responsible for the final check.

Ready-made curtains need a different comparison

For ready-made curtains, check the stated finished width and drop, panel count and heading. A listing for one panel is not the same as a pair, and flat width is not the same as gathered coverage. Compare the combined available width with the fullness required for your installation.

If alterations are needed, confirm whether the fabric and construction can be altered appropriately and what the work will cost. Do not assume every heading, lining or decorative border can be changed without affecting the result. The ready-made curtains guide can help with that decision.

For unusual dimensions, a custom specification may be worth comparing. Read the custom-made curtain guide and request quotations on equivalent coverage, fabric and fitting rather than comparing only the initial panel prices.

When to request professional measurement

Bay windows, curved tracks, corner arrangements, unusually wide spans and high-level installations need more than a basic width-and-drop guess. The hardware may require dedicated components, bends, returns or support positions. Ask for the supplier's specialist measuring process or a site assessment.

Professional help is also appropriate when the support system is unstable, the mounting surface is uncertain or the desired light exclusion is demanding. Do not drill or modify fittings to make uncertain measurements work. The installation plan should be resolved before production.

Final checks before you approve the order

1. Confirm every opening is clearly identified.

2. Use one labelled unit throughout the schedule.

3. Separate opening size, hardware span and finished curtain size.

4. Confirm the heading and drop starting point.

5. State the desired finish and number of layers.

6. Agree who calculates fullness and fabric allowances.

7. Record obstructions and any uneven measurements.

8. Approve the final specification in writing before cutting.

Send your photographs and measurement schedule through the Curtains Kenya contact page if you need clarification. Good measurement is not about adding as many allowances as possible. It is about giving the maker accurate, clearly labelled information so the finished curtains fit the agreed installation.