A curtain size calculator should not hide its sewing assumptions. The right curtain size for a window depends on the fitted hardware and chosen finish. The window opening, fitted track, finished curtain, ready-made panel and fabric roll are different measurements. Mixing them can leave a curtain too short, too flat or short of fabric.
To check curtain size for window openings, the quick calculator uses centimetres, two panels and 2× fullness. It gives finished panel dimensions. Fabric metres, headings, hems, pattern matching and cost require the separate manual checks below.
Calculate curtain size and fabric
Measure the fitted rod or track across its usable length, excluding decorative ends. Measure the finished drop from the fixing reference required by the chosen heading to the exact lower edge you want. Copy the fabric width and vertical pattern repeat from the current product information.
How do you calculate curtain size?
Start with the fitted rod or track, not only the glass or masonry opening. A track may extend beyond the window so the open curtains can sit partly away from the glass. Its final position also changes the drop.
The basic size calculation is:
- combined finished curtain width equals track width multiplied by fullness;
- finished width per curtain equals combined width divided by the chosen number of curtains; and
- ready-made panel count equals combined width divided by the labelled flat width of one panel, rounded up.
The result is a width check, not a recommendation. Heading tape, eyelets, rings, hooks, wave systems and pinch pleats do not all use width in the same way. Ask the maker or supplier to confirm the compatible fullness before you buy.
The Dunelm measuring guide measures the usable pole or track width and changes the drop reference for eyelet and pencil-pleat curtains. The India-based House of Ekam calculator also changes its result by fitting type and labels its result as a reference. These examples support keeping the hardware and heading inputs visible.
How to measure a window for curtains
Measure the actual opening first, then record the proposed hardware separately. Do not add an online extension to the opening and treat it as a site fact. Wall space, handles, furniture, air-conditioning units, ceiling details and adjacent corners can limit the track.
Use a stable tape and record at least these values:
| Measurement | Where to measure | Why it matters |
|---|---|---|
| Opening width | Finished edge to finished edge | Base condition before hardware is planned |
| Usable track width | Working end to working end, excluding finials | Coverage width used by the calculator |
| Mounting reference | Exact top, eye, hook or track reference | Starting point for the finished drop |
| Finished drop | Mounting reference to sill, floor or chosen end | Final curtain length before sewing allowances |
| Side space | Each end of the proposed track | Open-curtain stack and nearby conflicts |
| Floor variation | Drop checked at more than one point | Reduces surprises on an uneven floor |
Record whether the curtain opens from the centre, stacks to one side or uses more than two leaves. Check every repeated window. Similar-looking openings can have different widths, levels or obstructions.
How to calculate curtain fabric
Fabric quantity needs the finished size plus sewing information. For conventional fabric hung vertically, work through this manual sequence:
- divide the combined finished width by usable fabric width and round up to whole fabric drops;
- add the heading and hem allowances to the finished drop;
- when there is a vertical pattern repeat, round each cut length up to a complete repeat;
- multiply the cut length by the whole number of drops and identical openings;
- apply the entered order allowance; and
- round the order up to the next tenth of a metre.
The Sailrite curtain calculator exposes width, finished height, hem, fabric width, fullness and vertical repeat as separate inputs. Sew Helpful likewise reports whole widths, cut drops and pattern-adjusted drops. Morris & Co. states that its conventional calculation is not suitable when the fabric is used sideways. These manual cutting methods go beyond the finished-size estimate above.
| Input | Use current information from | Do not assume |
|---|---|---|
| Fullness | Heading and track supplier or curtain maker | One ratio fits every fabric and heading |
| Fabric width | Product label or current data sheet | The nominal roll width is fully usable |
| Pattern repeat | Current fabric information and physical check | A patterned fabric behaves like plain fabric |
| Top allowance | Approved heading construction | Every heading needs the same turn-in |
| Hem allowance | Approved make-up detail | Every weight and drop uses one hem |
| Extra allowance | Maker’s cutting and order plan | A generic waste percentage is always enough |
Worked curtain fabric example
Assume a fitted track is 240 centimetres wide. The approved heading uses two-times fullness, so the combined finished curtain width is 480 centimetres. A pair would target 240 centimetres of finished width per curtain.
The selected fabric is 140 centimetres wide. Dividing 480 by 140 gives 3.43, so the calculation needs four whole fabric drops. Those drops provide 560 centimetres before gathering, which creates an actual ratio of about 2.33 against the 240-centimetre track.
Assume a 250-centimetre finished drop, 10 centimetres for the top and 20 centimetres for the hem. The unadjusted cut length is 280 centimetres. If the vertical pattern repeat is 64 centimetres, each drop rounds up to five repeats, or 320 centimetres.
Four drops at 320 centimetres require 12.8 metres before extra allowance. A stated five-percent allowance produces 13.44 metres, which this manual example rounds to 13.5 metres. At a current fabric price of ₹800 per metre, the fabric-only amount is ₹10,800.
This example does not include lining, interlining, heading tape, buckram, stitching, hooks, rings, track, installation, transport, tax or pattern placement beyond repeat alignment.
What changes when the fabric has a pattern?
A vertical repeat means adjacent drops may need extra length so the design aligns across seams. For this manual method, round each cut drop to a whole repeat. That is a transparent planning allowance, not a cutting plan.
Half-drop patterns, engineered borders, large motifs and centred designs need more decisions. The maker may need an extra repeat to choose the starting position. The fabric may also arrive with a usable width smaller than its labelled width because of selvedges or flaws.
Do not cut from the calculator alone. Check the physical roll, dye lot, direction, repeat, half-drop status, panel sequence and seam plan. Once patterned fabric is cut, a measurement correction may require a new order rather than a small adjustment.
Ready-made panels or made-to-measure curtains?
The same measured opening can produce different buying checks. Use the panel result only for products sold by flat panel width. Use the fabric result when a maker will cut and sew the curtains.
| Buying route | Check first | Quantity to confirm | Confirm before paying |
|---|---|---|---|
| Ready-made panels | Labelled panel width and finished length | Whole panels needed for the entered fullness | Heading fit, usable width, panel joins and return terms |
| Made-to-measure curtains | Approved heading, finished size and fabric data | Whole drops, adjusted cut length and order metres | Cutting plan, seams, lining, stitching and installation |
| Existing curtains | Actual finished width and drop | Whether the current set covers the new track | Heading compatibility, alterations and fabric condition |
Do not compare only the fabric metre cost with a finished ready-made price. A fair comparison includes sewing, lining, hardware, installation, transport, tax and the risk of an unsuitable size.
How to use the curtain size calculator
Uses 2× fullness split across two panels. These are finished dimensions; fabric ordering also needs hems, headings and pattern repeat. Use the short form above for the initial measurement. Check your quotation PDF. Confirm the measurement basis and included work with the vendor before comparing prices.
How should curtains appear in a quotation?
Ask for one schedule per opening. Give every opening a room and reference. Record measured track width, finished drop, opening direction, heading, panel count, fabric identity, colour or dye lot, usable width, repeat, lining, make-up, hardware and installation.
| Quotation line | Check before accepting it |
|---|---|
| Main fabric | Product, width, repeat, metres, rate and tax basis |
| Lining or interlining | Exact product, separate metres and construction |
| Sewing | Heading, hems, seams, pattern matching and tolerance |
| Hardware | Track or rod, brackets, runners, hooks, rings and controls |
| Site work | Measurement, access, drilling, fixing, protection and making good |
| Delivery and installation | Transport, floor access, hanging, dressing and final adjustment |
| Handover | Cleaning method, spare components, warranty and defect response |
Use the Mumbai cost guide to define the complete budget. Check actual offers with the PDF quote checker.
Curtain measurement questions
What size curtains do I need?
You need the finished drop and enough combined finished width for the fitted rod or track under the approved fullness. Ready-made sizes must satisfy both numbers. Do not choose from the window opening alone.
How do I calculate curtain width for a window?
Confirm the fitted rod or track width, then multiply it by the approved fullness ratio. Divide the combined width by the number of finished curtains when a maker needs a per-curtain target.
How much curtain fabric do I need?
Divide combined finished width by usable fabric width and round up to whole drops. Multiply those drops by a cut length that includes the finished drop, heading, hem and pattern-repeat adjustment. Add only the order allowance agreed with the maker.
Can I measure curtains in inches?
Yes. Curtain measurements in inches work when every linear input uses the same unit. Choose inches in the tool. It converts the fabric order to metres and yards because Indian fabric quotations may still be stated per metre.
Where can I check the quoted prices?
Use the PDF quote checker. It separates published context from collected observations and does not certify a fair price.
Where can I check the quoted prices?
Use the PDF quote checker. It separates published context from collected observations and does not certify a fair price.
What should you do before ordering?
Name every opening and remeasure it after final finishes where the project sequence allows. Confirm the track, heading, fabric direction, repeat, panel split and finished drop in writing. Ask the maker to issue a cutting and make-up schedule.
Use the single room area calculator for inside length multiplied by width. Wall area needs a separate height measurement.