How do you build trustworthy calculators for non-technical users?

Hey dev.to 👋 Quick question for folks who’ve built tools for non-technical users.

If you’re making a small web app where accuracy matters (calculators, estimators, simulators), what’s your go-to approach for:

handling “messy” inputs (rounding, edge cases, unrealistic values)

explaining the result without dumping math on the user

adding guardrails so people don’t misuse the output

I’m especially curious about patterns that keep the UI simple while still earning trust. What’s worked for you?