Building one focused calculator in the open (Next.js, honesty, and IndexNow)

Souhayb kamal dine — Sun, 03 May 2026 15:35:47 +0000

We run thecalcs.com—a big library of small, single-purpose calculators. Adding “one more page” is easy; building something trustworthy is the hard part. This is how we approached one tool end to end: stack, where we draw the line on accuracy, and how we nudge search engines when we ship.

The stack (boring on purpose)

The site is Next.js (App Router), with calculator logic in plain TypeScript modules and UI in React components. We keep the math in lib/-style modules so the same formulas are testable and aren’t hidden inside event handlers. Styling follows the rest of the product so every calculator feels like the same app, not a random widget.

SEO without gimmicks

Good URLs, clear titles, and useful copy beat tricks. After launch or bulk updates, we also use IndexNow so Bing (and other participating engines via the shared protocol) get a prompt that URLs exist or changed. It’s not a ranking hack—it’s a crawl hint. The full library lives at thecalcs.com; if you’re curious how we group tools, start from the calculators section and drill into a category.

Takeaway

A “simple” calculator is a product problem: clear inputs, defensible math, and transparent limits. The stack is there to make that repeatable.

If you’re building something similar, start with one narrow use case, document your assumptions, and ship. We’re always adding more on thecalcs.com.

DEV Community: Souhayb kamal dine

Building one focused calculator in the open (Next.js, honesty, and IndexNow)

The stack (boring on purpose)

SEO without gimmicks

Takeaway