Gym-Math-Calculator

Inspiration

As someone who lifts regularly, I’m always trying to track progress — whether that’s figuring out how to load the barbell, estimate my one-rep max, or know when it’s time to move up in dumbbell weight. I wanted a tool I could actually use in the gym that was simple, fast, and accurate. That’s where the idea for Gym Math Calculator came from.

What It Does

The site includes three useful tools:

🏋️‍♂️ Plate Calculator
Input your barbell and target weight, and it tells you exactly which plates to load on each side.
🧠 Max Rep Estimator
Based on the Epley formula, this estimates your one-rep max based on the weight you lifted and how many reps you hit.
💪 Dumbbell Progress Checker
This one helps you decide if you should go up, stay the same, or drop dumbbell weight based on how well your last set went.

Everything runs in the browser with no install required.

How I Built It

I built the whole project using:

HTML
CSS (including Google Fonts for styling)
JavaScript (vanilla, no frameworks)

Everything is contained in a single index.html file and deployed through GitHub Pages. I also made sure it works well on both desktop and mobile.

Challenges I Ran Into

I originally wanted to do something more complex but realized keeping it simple made it more useful. One challenge was making sure each calculator gave clear and readable output. I also had to decide the best way to structure the logic — especially for the dumbbell recommendation.

I recorded the demo video without voice so I could show it in action clearly and then explained the features in writing.

Accomplishments I'm Proud Of

This is one of the first projects I’ve made that solves a real problem I have. It feels good knowing I can actually use it to improve my workouts. The design is clean, the logic works, and it’s easy to update or expand later.

What I Learned

Structuring logic clearly in JavaScript
Building user-friendly input/output flows
Making a functional single-file project with no setup
Using GitHub Pages to host it live
Writing project documentation and submitting to Devpost

What's Next

I'd like to add a feature that tracks progress over time or saves your last lift history. I may also include a calorie or protein calculator based on gym goals.