Royal Plast: window quotes with price and sketch, no manual math

This is a case study of the quote portal I built for Royal Plast, a company from Montenegro that makes custom windows and doors. The company has no public website: the portal runs on its subdomain, and the company uses it to create quotes for businesses and private customers.

Client and context

Royal Plast sells custom windows and doors. Every customer enquiry ends in a quote, and a quote for windows is not a list of items with a total: every item has its own dimensions, opening direction, glass type and extras. I built the portal in 2025. It runs online, the company uses it, and more than one person can work in it.

Problem

Quotes were made by hand. A custom window has no price until everything is chosen: dimensions, opening type, glass, roller shutter, drip cap, insect screen. Extras are not added as fixed amounts; they are calculated per square meter or per linear meter, so the same math was done again for every enquiry.

The second part of the problem was the description. A finished item was described to the customer in words, "single sash, left sash tilt, right sash tilt and turn", which a window fitter understands and a customer often does not. With custom windows, a misunderstanding cannot be fixed by putting the product back on the shelf: the window has already been cut to those measurements.

Constraints

The hardest part was the window drawing and the surcharge calculation. The drawing has to come from the same dimensions entered for the price, with measurements, so it matches that exact item. Surcharges depend on the window type and on the extra: low emissivity glass and an insect screen are added to the base price, and each has a defined price per square meter or per linear meter.

The second constraint was prices. The client changes them often, so no price could be written into the code. Everything comes from a price list the company edits itself.

Solution

A quote in three steps

A quote is created in three steps: customer, items, review. In the first, you pick an existing customer or add a new one, a business or a private person. In the second, you add items, with the total before VAT at the top, changing as you choose. In the third, you see the whole quote before the PDF is created, so mistakes are caught on screen.

A price that calculates itself

Each item starts from an article in the price list. Articles are found by name while you type, and the price list can be filtered to windows or doors. On top of the base price, the portal adds surcharges: for the glass type (float is the default, while low emissivity, "four seasons" and "Stop Sol" glass each have a surcharge per square meter), for the insect screen by type, and for the roller shutter and drip cap. Every surcharge is shown next to the option, so whoever creates the quote knows why the price changed.

A window sketch instead of a description

For each item, the portal draws a sketch of the window from the dimensions entered, with measurements and the opening direction marked for the left and right sash (tilt, or tilt and turn, for example). The sketch sits on the quote next to the price. The customer sees the window they are ordering instead of picturing it from a description.

A PDF quote that looks professional

The final output is a PDF with the company logo, the company details and the customer details. At the bottom are the net amount, VAT at the 21% rate that applies in Montenegro and the total, followed by how long the quote is valid and fields for signatures. A note can be added to the quote for anything agreed outside the price list.

Customers and quote history

The portal keeps a record of customers, both businesses and private persons. Every quote stays in the list with its number, customer and date, and can be downloaded again at any time without being recreated. The home page has shortcuts to a new quote, customers and items, and a list of the five most recent quotes.

One item, as an example

The screenshots show a test quote, with prices as they were in the price list at the time:

Part of the item	Value
Article	single sash window, 100 x 100 cm, 2 seals, double glazed, white
Base price from the price list	150.00 EUR
Extras	roller shutter, drip cap, fixed insect screen (30 EUR/m²)
Glass	"four seasons", surcharge 7 EUR/m²
Total before VAT	277.00 EUR
VAT 21%	58.17 EUR
Total with VAT	335.17 EUR

By hand, an item like this means calculating each extra from the window area and adding it up. In the portal, you pick the extras and the amount is on screen before you move on to the review.

What the price list holds

Each article in the price list has a name, dimensions, type (single or double sash), color, number of chambers and a price, and is marked as a window or a door. The company adds articles and changes prices itself, and the next quote uses the new price list. There is no limit on the number of articles.

Technologies and why

The portal is built in PHP, MySQL, JavaScript and HTML and runs on the company's subdomain, online, so nothing has to be installed on the company's computers. The price changes on screen while extras are chosen, and the PDF carries the same data as the review.

Result

A quote that used to be made by hand now comes out finished, with the price, a sketch of every item and VAT, in a form that can be sent to the customer or printed and signed. The customer sees the window before ordering it, so misunderstandings are caught on paper, not in the workshop. All quotes are in one place and can be downloaded again at any time (as of October 2026).

Sources

The standard VAT rate of 21% in Montenegro has applied since January 1, 2018, according to KPMG Montenegro's overview of the VAT law amendments; checked on October 5, 2026.