Coupon Calculator, A lightweight Flask app

I made this lightweight Flask app designed to make checkout math faster, clearer, and more accurate. It helps users calculate the discount amount and final price before making a purchase or a cashiers who have to do coupons manually (like me), while keeping the logic strict enough to prevent bad input and messy rounding.

[The link to the live app is below:]
Open Coupon Calculator

Why I built it

I’ve been working toward becoming a better developer and engineer, and one of the biggest lessons I’ve learned and believe is that real problems often lead to the best projects. I recently started a job as a cashier, and I'm not good at math in the slightest and i deal with dyscalculia, so discounts and price calculations can become confusing, especially during busy checkout moments or when helping older shoppers who are not comfortable with technology.

I needed something simple, reliable, and easy to use that could reduce mental math mistakes and make pricing more transparent. That idea became this calculator.

What the app does

The app allows a user to:

• enter an original price
• choose a percentage discount or a fixed discount amount
• validate the inputs before calculating
• see exactly how much money is saved
• view the final price after the discount is applied

It is built for everyday shopping scenarios where the user needs a quick and trustworthy estimate.

Key features

• Percentage discounts up to 100%
• Fixed-amount discounts
• Negative-value validation
• Protection against invalid numeric input
• Currency-safe rounding to two decimal places
• Clear, simple interface for fast use

Why this project matters to me

This project is a practical tool built from a real-world need, and it reflects the kind of developer I want to be, All I want is to solve problems with simple, useful solutions and maybe something i make will eventually help some on but, probably not.