Built a Free Calculator Site with Regra de 3 + Hours Worked Tools

Hey Indie Hackers 👋

I love building small tools that solve everyday problems. So I built calculadora3.com.br — a site with two simple, free calculators:

1️⃣ Regra de 3 Online — quickly solve cross-multiplication problems (super useful for students and quick percentage calculations).
2️⃣ Calculadora de Horas Trabalhadas — calculate how many hours you worked between two times (helpful for freelancers, shift workers, and HR tasks).

Both tools run directly in the browser, no installs or downloads needed.

📊 Early results:

• 2,000+ calculations run in the first month

• Average session: 3 minutes (people often use both calculators)

• Most requested feature: ability to save or print results

🛠️ Next steps:

• Add dark mode and mobile-optimized layout

• Add new calculators (percentage, overtime pay, simple interest)

• Translate site to English and Spanish

I’d love feedback from this community:

• What other calculators would you like to see?

• Should I add a mini API so other sites can embed these calculators?

Thanks for reading, and feel free to try it out: calculadora3.com.br 🙏