# Product Context

## Why this project exists?
Gridfinity is a popular modular storage system. While the standard is well-defined (42x42x7mm), users often need to:
1. Figure out how many baseplates fit in a drawer.
2. Determine the maximum height of bins for a specific drawer depth.
3. Scale the system slightly to perfectly fill a drawer that doesn't fit a whole number of 42mm grids.

## User Experience
- **Input-First:** Users should immediately see where to enter their dimensions.
- **Instant Feedback:** Results should update as they type.
- **Flexibility:** Toggle between mm and inches easily.
- **Precision:** Clear output showing "Full Grids" and "Vertical Units".

## Success Criteria
- Accurately converts between units.
- Correctly calculates bin height while accounting for baseplate/bin-bottom thickness.
- Provides clear instructions for "fractional" fits (e.g., if a drawer is 100mm, it fits 2.38 grids).