BMI Calculator
A BMI calculator built with Flutter. Height and weight in, category and guidance out. Small by design — the exercise was making a two-input form genuinely pleasant to use, with unit handling, input validation and clear result presentation.
- Role
- Sole developer.
- Year
- 2023
- Stack
- Flutter, Dart, BMI Calculation, UI/UX
The problem
A two-field form is the hardest place to hide sloppiness. Unit confusion, unvalidated input and a bare number as output are all immediately visible, so the whole exercise is in the details most implementations skip.
How it was built
01Unambiguous units
Metric and imperial are explicit rather than inferred, because a height of 70 is either a very short adult or a normal one depending on the unit and guessing wrong makes the result meaningless.
02Validation before calculation
Physically impossible values are rejected at the input with an explanation, rather than producing a confidently wrong BMI. A calculator that returns a number for nonsense input teaches the user to distrust every number it returns.
03Result with context
The output includes the category and what it means, not just a figure. A bare number requires the user to go and look up what it signifies, which is the actual question they had.
Stack decisions
Why each piece was chosen, rather than just what was used.
Flutter
Cross-platform from one codebase, with tight control over the form layout and input behaviour.
Dart
Type safety on numeric input handling, where unit conversion errors are the main risk.
What it does
- Metric and imperial input with explicit units
- Input validation with clear error messages
- Instant BMI calculation with category
- Plain-language explanation of the result
Related work
Building something similar?
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