I Shipped 2,000+ Free Calculators With Zero Backend. Here's What I Learned.

The headline states that the author shipped over 2,000 free calculators without any backend support. The site features various calculators such as income tax, loan installments, BMI, and unit conversions. All these calculators are built using pure client-side JavaScript, with no database, tracking, or sign-up required. The author emphasizes that the success of a calculator depends solely on its accuracy.

To ensure correctness, the author validates each formula against an official source before deploying it. For instance, the income-tax calculator adheres strictly to Indonesia's progressive tax brackets. The author stresses the importance of treating formula changes like database migrations to maintain accuracy. When working with money, the author advises using integer units and formatting only at the final display stage to avoid floating-point errors.

The author also highlights the use of Intl.NumberFormat for locale-specific formatting, such as Indonesian numbering conventions. The site employs programmatic SEO, generating the 2,000+ pages at build time and serving them as static HTML, which results in instant load times, cheap hosting, and easy crawlability. The author also mentions that the site does not require user accounts, eliminating password resets, session bugs, and user data leaks.

However, this trade-off means that users cannot sync their history across devices. The author concludes by stating that every input to their calculators is processed through a consistent pipeline, including formatting removal, parsing, range clamping, and providing helpful error messages for invalid inputs.