This wallpaper calculator prices a wall from its width and height, and the shopper chooses whether to type them in centimetres, feet and inches, or inches. Each colour is a Shopify variant, and that variant's price in Shopify is the price per square foot. The calculator works out the wall's area and multiplies it by that rate.
This is a look inside the Wallpaper Multi-Unit calculator on our Shopify demo store. It's built with Appify Custom Product Options.
If you're setting up a wallpaper store from scratch, start with how to sell custom wallpaper by wall size. This article is about one calculator in it: the one that lets customers in different countries measure their wall their own way.
What it does
The calculator opens on three colour swatches (blue, pink and yellow) and a units dropdown set to centimetres. The shopper types a width and a height, and the price summary shows the area and the total.
In plain words, you set each colour's price per square foot as its variant price in Shopify. The calculator turns the wall into square feet and multiplies. Nothing else adds to it.
Why a multi-unit wallpaper calculator is hard to build, and how Appify Custom Product Options handles it
- Your customers measure in different units. A shopper in one country has a wall in centimetres, another has feet and inches, and a third has plain inches. The calculator carries all three, and only the boxes for the unit they picked show up. Visibility rules do the switching.
- Three sets of numbers have to become one area. Centimetres, feet and inches all need to land on the same square feet. Three pricing variables do it in steps, so the price formula stays one short line.
- Feet and inches arrive in two boxes. A wall of 8 feet 6 inches has to become 102 inches before it can be multiplied. The formula adds the feet times 12 to the inches.
- Each colour can carry its own rate. The swatches are the product's colour variants in Shopify, and each variant's price is that colour's price per square foot. The rate follows the colour without a second option.
- The order has to keep the wall size. The width, the height and the colour all stay on the order, and the shopper can edit them from the cart. Reordering later brings every choice back.
One price, worked out
Here's the blue wallpaper for a wall 300 cm wide and 250 cm high, with prices in dollars. The numbers come straight from the calculator's price summary.
- Area: 300 by 250 cm is 80.73 square feet.
- Rate: the Blue variant is priced at 29.00 in Shopify, so blue costs 29.00 per square foot.
- Total: 80.73 square feet at 29.00 comes to 2,341.15.
Whichever unit the shopper picks, the variables convert it to inches and then to square feet before the price is worked out.
The design decisions
One units dropdown, three sets of boxes
A dropdown beside the wall-size heading offers cm, ft/in and in. Each unit has its own dimensions option with a width and a height. Feet and inches get four boxes: width in feet and inches, then height in feet and inches.
Rules show only the unit that was picked
Each set of boxes has a rule that shows it when the dropdown holds its unit. Pick inches and the centimetre and feet boxes disappear. A hidden option is left out of the price and out of the cart, so a stale number in a box you can't see never reaches the total.
Each unit is its own set of boxes, a rule that shows it, and a branch in the width and height variables. The price formula only ever reads the area, so it stays the same.
Three variables turn any unit into an area
The first variable is the width in inches. It checks which unit is picked: centimetres are divided by 2.54, feet and inches become feet times 12 plus inches, and inches are used as typed. The second does the same for the height.
The third multiplies the two and divides by 144 to get square feet. Variables run top to bottom, so each one can read the ones above it.
The price formula is one line
The total price formula is VAR("AREA_FT2") * VAR("SHOPIFY.PRICE"): the area in square feet times the price of the selected variant. That's all it says.
So in Shopify you don't price a wall. You price a square foot, once per colour, as that variant's price. The calculator does the rest for any wall size.
Built for a design that repeats across the wall
This example assumes the wallpaper repeats horizontally, so the price is the plain area. Wallpaper with a different repeat is a change to the size variables, not a different setup:
- Repeats across: keep the plain area, or round the width up to whole repeats if every panel has to be a full one.
- Repeats down: round the height up to the next full pattern repeat, so a drop never ends mid-motif.
- Repeats both ways: round the width and the height, and the area becomes whole repeats across times whole repeats down.
Each rounding is one CEILING in a formula, reading the repeat size from the product. For a worked example, see how the wallpaper calculator priced by material rounds the width up to the material's width.
The colours are the product's own colours
The colour option is an image swatch that reads the colours from the Shopify product, with each colour's own picture. Choosing a swatch selects that variant, so the rate follows the colour. To change what a colour costs per square foot, edit that variant's price in Shopify and the calculator picks it up. Add a colour to the product in Shopify and it shows up as a swatch.
Wall size is required, and the summary stays short
Whichever unit is showing is a required field, so the shopper can't add to cart without a wall size. The price summary lists two lines: the area, shown in square feet, and the total.
What arrives with the order
The calculated price goes to checkout. Cart properties carry the wall size in the unit the shopper chose, and the colour is the cart variant. A wall typed in feet and inches arrives in feet and inches, and one typed in centimetres arrives in centimetres. The two hidden sets of boxes stay off the order, so your team works from the customer's own measurements. The same details show on the app's Orders page.
This calculator allows Edit options from the cart, so a shopper who mistyped a width fixes it without starting over. When they come back for another room, Appify Reorder brings the first order back with every choice filled in, where Shopify's own Buy again drops them.
Make it yours
- Add extra for trimming waste. Multiply the area variable by 1.1 and every wall is priced with 10 percent extra.
- Set a minimum order price. A minimum price on the total keeps a small wall from going out under your floor.
- Price by material as well. Add a material option and a pricing table keyed on it, then let the formula read the rate from the table.
Get this calculator
Ask Chat with AI to build it in your own words. For example:
"Build a wallpaper calculator priced by wall area."
"Add a Units dropdown with cm, ft/in and in."
"For each unit, add a required width and height option that only shows when that unit is picked. For ft/in, use separate feet and inches boxes."
"Add variables that turn the width and height into inches, then the area in square feet."
"Price the product as the area in square feet times the selected variant's price. Each colour variant's price is its price per square foot."
Chat with AI writes the options, the variables and the rules. Check the price in the preview against a wall you've priced by hand before you publish.
FAQ
How do you price wallpaper by wall size on Shopify?
Add width and height options, turn them into an area with a pricing variable, and multiply by your rate. The calculator shows the total as the shopper types.
Can customers enter the wall in centimetres or feet and inches?
Yes. Add a units dropdown and a set of boxes for each unit. Rules show only the boxes for the unit that was picked, and variables convert every unit to one area.
Can each wallpaper colour have a different price?
Yes. Make each colour a Shopify variant and set its price to that colour's price per square foot. The formula reads the price of the variant the shopper chose.
Do I need a variant for every wall size?
No. The wall size comes from the width and height the shopper types, and the price comes from the formula.
Which unit does the order show?
The one the shopper chose. A wall entered in centimetres arrives in centimetres, and one entered in feet and inches arrives in feet and inches.
Can the shopper change the wall size after adding to the cart?
Yes, when the calculator allows it. They use Edit options in the cart and the price updates.
Every wall, priced in the unit they measured.
Whatever you sell, however you price it · The last options app you'll shop for