Curtain prices depend on things a price list can't show, like how much fabric the gather uses and what goes along the top.
This is a look inside the Customizable Curtains calculator on our Shopify demo store. It's built with Appify Custom Product Options. Here's what it does, why it's built the way it is, and how to make one like it for your own store.
What it does
The shopper picks centimetres or inches, types the window width and the curtain drop, and chooses a heading, a gather, single or pair, and a side finish. They can name the window too. The price updates as they go.
In plain words, the price is the fabric, plus the heading, plus the side finish. The fabric part grows with the width and the gather, and the rate per metre steps up for longer drops.
Why a curtain calculator is hard to build
- Shoppers measure in different units. Some think in inches, some in centimetres. The calculator takes either and converts both to metres before any math runs.
- The fabric isn't the window width. A 2.5x gather needs two and a half times the width in fabric. The price follows the fabric used. A pricing variable holds that fabric width for the fabric and heading costs to reuse.
- Longer drops cost more per metre. The rate comes from a pricing table of drop bands. A fixed add-on price can't do that.
- Some choices price by the metre, some by the curtain. Pencil pleat tape is charged along the full fabric width. Hemmed sides are charged per curtain, so a pair pays twice. One formula handles both.
- The order has to survive the cart. The customer can fix a measurement from the cart, and a reorder comes back with every choice filled in.
One price, worked out
Here's the example above, with prices in dollars. The window is 60 inches wide with an 84 inch drop, pencil pleat with 2 inch tape, 2.5x gather, a pair with hemmed sides.
- Fabric width: 60 inches is 1.524 metres, rounded up to 1.6. At 2.5x gather, that's 4 metres of fabric.
- Fabric rate: an 84 inch drop is about 213 cm, which falls in the 150 cm band, at 5.60 a metre. The fabric comes to 22.40.
- Heading: 2 inch pencil pleat tape at 2.25 a metre, along 4 metres, is 9.00.
- Sides: hemmed sides at 3.95 a curtain, for a pair, is 7.90.
22.40 for fabric, 9.00 for the heading and 7.90 for the sides. The calculator shows a total of 39.30.
The design decisions
Convert every size to metres first
Two pricing variables turn the width and the drop into metres. Each checks the unit the shopper picked and applies the right conversion. Everything after that works in one unit, so the rest of the pricing never needs an inches version.
The shopper just types the number they measured.
Limits that follow the unit
The width and drop fields have limit rules, a kind of visibility rule. Pick centimetres and the width accepts 50 to 2000. Pick inches and it accepts 20 to 787. The drop follows the same pattern.
Shoppers can't order a size you don't make, in either unit.
The price follows the fabric, not the window. Width, gather, drop band, heading and sides each feed a named step, and one formula adds them up. Change a rate once and every size reprices correctly.
Round up, then multiply by the gather
The width in metres is rounded up to the next tenth of a metre, then multiplied by the gather. That result is its own pricing variable, the total fabric width.
The fabric cost and the heading cost both read that one number. Change the gather and both move together.
A table for the drop, not a formula
The price per metre comes from a small pricing table with three drop bands. Its lookup mode is nearest lower, so any drop takes the rate of the band it falls in.
A supplier's price list usually comes as bands like these. The table holds them as written, and changing a rate is a one-cell edit.
Headings that price per metre
The heading dropdown gives each heading its own price per metre of fabric. Pencil pleat reads its price from a second choice, the tape width, which only appears once pencil pleat is picked. Each heading's detail choices, like eyelet colours, only appear once that heading is picked.
The shopper only sees the choices that apply to the heading they picked.
A total built from named parts
The final price formula is three variables added together: fabric, heading and sides. Each part can be checked on its own. If a price ever looks wrong, the Troubleshoot tab in the formula editor shows the value of every step.
What arrives with the order
The calculated price goes to checkout on one cart line. No size becomes a Shopify variant.
The order shows every choice, from the unit and the measurements to the heading, gather and sides, plus the window name. That makes a job with five windows easy to pack and label.
Customers can tap Edit options in the cart to fix a measurement without starting over. Later, Appify Reorder brings the curtain back with every choice filled in, where Shopify's own Buy again drops them.
Make it yours
- Price by fabric as well as drop. Add a fabric choice and turn the drop table into a grid, with fabrics down the side and drop bands across.
- Add lining. A lining dropdown priced per metre of fabric works just like the heading.
- Sell the rod with it. Attach rods or tracks as linked add-on products, so they keep their own stock and price.
Get this calculator
Start with Chat with AI and describe it in your own words. For example:
"I sell made-to-measure curtains. Customers choose cm or inches and enter window width and drop. They pick a heading, a gather from flat to 3x, single or pair, and a side finish. Fabric price is the width times the gather, times a rate per metre that depends on the drop. Headings add a price per metre of fabric. Side finishes are priced per curtain."
It builds the options, the drop table and the pricing formula. Then adjust the rates to your own price list. For the wider picture, read how to sell fabric, rugs and curtains by size on Shopify.
FAQ
Can a Shopify curtain calculator take both inches and centimetres?
Yes. The shopper picks a unit, and pricing variables convert the size to metres before the price is worked out. Field limits change with the unit too.
How does the gather change the price?
The gather multiplies the fabric width. A 2.5x gather on a window that rounds to 1.6 metres uses 4 metres of fabric, and both the fabric and the heading are priced on that.
Can the fabric rate depend on the curtain drop?
Yes. A pricing table holds a rate per drop band, and the calculator takes the rate of the band the drop falls in.
Does a pair cost double?
Only for the parts priced per curtain, like the side finish. The fabric follows the window width, whichever you choose.
Do I have to write the formulas?
No. Describe your pricing to Chat with AI and it writes them. You can still edit any of them by hand.
Every window, priced to the metre of fabric.
Whatever you sell, however you price it · The last options app you'll shop for