Curtain Calculator
Curtain Fabric Calculator
Enter your window and curtain details to estimate the fabric required.
The width of your curtain track or pole.
From the top of the track/pole to where the curtain should end.
How gathered you want the curtains. 2x is common.
Will you have one or two curtain panels?
Extra fabric for the curtain heading (e.g., pencil pleat tape, eyelets).
Fabric turned up for the bottom hem (e.g., 7.5cm double hem = 15cm).
Fabric for each side hem (e.g., 2.5cm double hem per side = 5cm). Total for one panel will be double this.
The width of the fabric roll you intend to buy.
Vertical distance before the pattern repeats (0 for plain fabric).
Results
Fabric Usage Breakdown
| Item | Details | Value (cm) |
|---|---|---|
| Window Width | – | – |
| Fullness | – | – |
| Total Width Needed | – | – |
| Width per Panel (inc. side hems) | – | – |
| Fabric Widths per Panel | – | – |
| Total Fabric Widths | – | – |
| Finished Drop | – | – |
| Cut Drop (inc. hems & pattern) | – | – |
| Total Fabric Length | – | – |
Table showing the calculation breakdown for your curtains.
Fabric Length Allocation (cm per width)
Chart illustrating the components of the cut drop length per fabric width.
What is a Curtain Calculator?
A Curtain Calculator is a specialized tool designed to help you determine the amount of fabric required to make curtains for your windows. It takes into account various factors such as window dimensions, desired fullness, hem allowances, heading types, and fabric width, as well as pattern repeat if you’re using patterned fabric. Instead of complex manual calculations, a Curtain Calculator simplifies the process, reducing the risk of buying too little or too much fabric.
Anyone planning to make or order custom-made curtains should use a Curtain Calculator. This includes DIY enthusiasts, home sewers, interior designers, and even those ordering from curtain makers to verify the fabric amount. Common misconceptions are that you only need fabric matching the window’s area or that all fabrics require the same amount; the Curtain Calculator addresses fullness and pattern matching, which significantly impact fabric needs.
Curtain Calculator Formula and Mathematical Explanation
The Curtain Calculator uses several steps to arrive at the total fabric needed:
- Total Width Required: First, it calculates the total flat width of fabric needed before gathering: `Total Width = Window Width * Fullness Ratio`.
- Width per Panel: If you’re making a pair, this total width is divided by two: `Width per Panel (raw) = Total Width / 2` (or just Total Width for a single panel). Then, side hems are added: `Finished Panel Width = Width per Panel (raw) + (2 * Side Hem Allowance)`.
- Number of Fabric Widths: Based on the width of your chosen fabric, the calculator determines how many ‘widths’ or ‘drops’ of fabric are needed per panel: `Widths per Panel = Ceiling(Finished Panel Width / Fabric Width)`. For a pair, this is multiplied by two.
- Cut Drop Length: The length of each fabric piece (cut drop) is calculated: `Basic Cut Drop = Finished Curtain Drop + Heading Allowance + Bottom Hem Allowance`.
- Pattern Repeat Adjustment: If using patterned fabric, the cut drop is adjusted to ensure patterns align across widths: `Adjusted Cut Drop = Ceiling(Basic Cut Drop / Pattern Repeat) * Pattern Repeat` (if Pattern Repeat > 0). If plain, `Adjusted Cut Drop = Basic Cut Drop`.
- Total Fabric Length: Finally, the total length of fabric is: `Total Fabric = Total Number of Widths * Adjusted Cut Drop`. This is usually converted to meters or yards.
Variables Table:
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Window Width | Width of the curtain track or pole | cm or inches | 50 – 500 cm |
| Finished Drop | Desired final length of the curtain | cm or inches | 50 – 400 cm |
| Fullness Ratio | How much gather the curtain will have | Multiplier | 1.5 – 3 |
| Heading Allowance | Extra fabric for the top heading | cm or inches | 5 – 25 cm |
| Bottom Hem | Fabric for the bottom hem (often double) | cm or inches | 10 – 20 cm |
| Side Hems | Fabric for one side hem (double it for total per panel) | cm or inches | 2.5 – 7.5 cm |
| Fabric Width | Width of the fabric roll | cm or inches | 110 – 150 cm |
| Pattern Repeat | Vertical repeat of the fabric pattern | cm or inches | 0 – 100 cm |
Our guide on choosing fabric can help you decide on fabric width and pattern repeats.
Practical Examples (Real-World Use Cases)
Let’s see the Curtain Calculator in action:
Example 1: Living Room Curtains (Pair, Plain Fabric)
- Window Width: 200 cm
- Finished Drop: 230 cm
- Fullness: 2x
- Type: Pair
- Heading: 10 cm
- Bottom Hem: 15 cm
- Side Hems: 5 cm (per side)
- Fabric Width: 140 cm
- Pattern Repeat: 0 cm (plain)
The Curtain Calculator would determine: Total width needed 400cm, 200cm per panel raw, 210cm finished per panel. This needs 2 widths of 140cm fabric per panel (total 4 widths). Cut drop is 230+10+15=255cm. Total fabric: 4 * 255cm = 1020cm or 10.2 meters.
Example 2: Bedroom Curtain (Single, Patterned Fabric)
- Window Width: 150 cm
- Finished Drop: 180 cm
- Fullness: 2.5x
- Type: Single
- Heading: 15 cm
- Bottom Hem: 15 cm
- Side Hems: 5 cm (per side)
- Fabric Width: 137 cm
- Pattern Repeat: 64 cm
The Curtain Calculator would work out: Total width 375cm, 385cm finished. This needs 3 widths of 137cm fabric. Basic cut drop is 180+15+15=210cm. With pattern repeat, adjusted cut drop is Ceiling(210/64)*64 = 4*64 = 256cm. Total fabric: 3 * 256cm = 768cm or 7.68 meters (you’d buy 7.7 or 7.75m, or even round up to the next full repeat length per drop depending on supplier).
For more on patterns, see our home decor ideas section.
How to Use This Curtain Calculator
- Measure Your Window: Accurately measure the width of your track or pole and the desired finished drop.
- Enter Dimensions: Input these into the “Window Width” and “Finished Curtain Drop” fields.
- Select Fullness: Choose how full you want your curtains (2x is standard).
- Choose Type: Select ‘Pair’ or ‘Single’.
- Enter Allowances: Input the fabric needed for heading, bottom, and side hems. Consider your curtain heading type.
- Fabric Details: Enter the width of your fabric and the pattern repeat (0 if plain).
- Calculate: The Curtain Calculator updates automatically, showing total fabric needed and intermediate steps.
- Review Results: Check the primary result (Total Fabric Needed) and the breakdown in the table and chart.
The results from the Curtain Calculator guide your fabric purchase. Always consider buying slightly more for safety.
Key Factors That Affect Curtain Calculator Results
- Window/Track Width: The starting point for all width calculations.
- Desired Fullness: More fullness means significantly more fabric width is needed.
- Finished Drop: Directly impacts the length of each fabric drop.
- Allowances (Heading & Hems): Add to the cut length of each drop. Larger hems or complex headings require more.
- Fabric Width: Narrower fabrics require more widths to cover the desired curtain width, potentially increasing waste if cuts are inefficient.
- Pattern Repeat: A large pattern repeat can significantly increase fabric consumption as each drop needs to be cut starting at the same point in the pattern, leading to more waste between cuts.
- Curtain Type (Single/Pair): Affects how the total width is divided and the number of side hems accounted for.
Understanding these helps you use the Curtain Calculator effectively and plan your sewing project.
Frequently Asked Questions (FAQ)
A: Fullness is the ratio of the total flat fabric width to the width of the curtain track or window. A 2x fullness means the fabric is twice the width of the track, creating standard gathers. More fullness (e.g., 2.5x or 3x) gives a richer, more luxurious look but uses more fabric. Our Curtain Calculator allows you to select this.
A: It’s wise to buy about 10% extra, especially with patterned fabrics or if you are new to sewing, to account for errors or pattern matching subtleties not fully captured by a basic Curtain Calculator.
A: It calculates the number of widths needed and the cut length, assuming you will join them with seams. It doesn’t add extra for the seam allowances themselves within the cut drop, but side hems are included.
A: You’ll need more widths to achieve the desired fullness, which the Curtain Calculator will show. This can mean more seams in your finished curtains.
A: Input the exact vertical repeat into the Curtain Calculator. Be prepared for potentially higher fabric requirements as more fabric might be ‘wasted’ between cuts to align the pattern.
A: Yes, but sheers often look better with more fullness (e.g., 2.5x or 3x). Adjust the fullness ratio accordingly.
A: The Curtain Calculator doesn’t account for shrinkage. If your fabric is prone to shrinking (like cotton or linen), consider pre-washing it or adding a small extra percentage to the drop length.
A: Eyelet curtains usually require more heading allowance for the stiffening buckram and the space above the eyelets. Check the instructions for your eyelet tape/rings, but 15-20cm is common. Input this into the Curtain Calculator.
Related Tools and Internal Resources
- How to Sew Curtains: A step-by-step guide to making your own curtains after using the Curtain Calculator.
- Choosing the Right Curtain Fabric: Understand different fabric types and how they affect your project and the Curtain Calculator inputs.
- Guide to Curtain Heading Types: Learn about pencil pleat, eyelet, tab top, and more, and how they impact fabric needs.
- Measuring Windows for Blinds and Shades: If you’re considering other window treatments.
- Home Decor Inspiration: Get ideas for your window treatments and room styling.
- More Sewing Projects: Explore other DIY sewing ideas for your home.