DEV Community: Brent

I built 73 free construction calculators with Next.js — and learned the hard way that Google won't index a new site just because it exists

Brent — Mon, 08 Jun 2026 22:05:39 +0000

Every construction calculator on the first page of Google has the same problem: you search "how much concrete do I need," land on the page, and before you can type a number you're fighting a cookie banner, a newsletter popup, an AI chatbot bubble, and three display ads that shift the layout while you're tapping.

So I built the version I actually wanted: ProjectCalc
— 73 free calculators for construction, home improvement, and DIY. No signup, no popups, no chatbot. It runs entirely in your browser and works on a 4G phone with one bar.

This post is half "Show Dev" and half a brutally honest field report on the part nobody warns you about: **getting a brand-new domain indexed by Google is its own engineering problem, and shipping good content is only step one.

What it is

73 calculators across the math contractors and homeowners actually need:

Carpentry — beam span, stair stringer, rafter length, floor joist span
Electrical — voltage drop, conduit fill, wire gauge, panel load (NEC)
Plumbing — drain, vent, and supply pipe sizing (IPC)
HVAC — Manual J heat load, BTU, duct CFM (ACCA)
Masonry — brick and block counts, mortar, rebar grids
Home & DIY — concrete, drywall, paint, mulch, gravel, tile
Finance — mortgage, loan, and car-payment calculators

Every calculator shows the formula, a worked example, common mistakes, and rules of thumb so you can sanity-check the result instead of trusting a black box.

The one feature I'm proudest of: a visual room sketcher that draws your room as you type the dimensions and pre-fills the matching calculator with the numbers — including L-shaped rooms with a corner bump-out. Draw the room once, get drywall sheets, paint gallons, and flooring square footage without re-entering anything.

The stack

Nothing exotic — boring on purpose, because boring is fast:

Next.js 16 (App Router), TypeScript
Vanilla CSS, no Tailwind — kept the bundle tight and the first paint instant
Static Site Generation — every calculator page prerenders to HTML, so there's no client round-trip to see content
Dynamic OG images via next/og on the edge runtime
100% client-side math — your inputs never leave the page; there's no backend to send them to
Vercel for hosting, auto-deploy on push to main

The calculators are defined as plain data objects — slug, inputs, a pure calc()
function, and prose fields — so adding a new one is a config entry plus a companion blog post, not a new route.

Now the part that hurt: indexing

I launched, submitted my sitemap to Google Search Console, and waited for the calculator pages to show up in search.

They didn't.

Weeks in, GSC told the story: 1 page indexed (the homepage), and ~120 pages stuck in "Crawled – currently not indexed." Another batch sat in "Discovered currently not indexed." Zero technical errors — no 404s, no robots blocks, no canonical issues.
Google was fetching the pages fine and then *choosing not to index them.

If you've never hit this wall, here's what I learned digging into it:

"Crawled – currently not indexed" is a verdict, not a bug.** It means Google fetched your page and decided it wasn't worth an index slot yet. You can't fix it with more schema or meta tags. I had valid JSON-LD, canonicals, breadcrumbs, the works. Didn't matter.
A new domain has almost no crawl budget.** When I pulled the actual last CrawlTime` for each URL via the URL Inspection API, the truth jumped out: Google had crawled most pages once near launch and then basically never came back. Every content improvement I shipped afterward — expanded prose, code citations, diagrams —Google had never seen, because it hadn't re-crawled. I was tuning a page nobody was re-reading.
The Indexing API doesn't work for normal pages.** I tried it. The official Indexing API is only for JobPosting and BroadcastEvent schema; for regular pages Google ignores it. My own crawl logs confirmed it triggered nothing.
What actually moves it:** the manual "Request Indexing" button in GSC (forces a re-crawl of the current version), plus — the real lever — backlinks and real traffic arriving together. A young domain with zero inbound links gives Google no reason to spend crawl budget or trust. This post is, candidly, part of that fix.

The lesson I wish I'd internalized on day one: on-page SEO is table stakes; it's not a growth strategy. You can have technically perfect pages and still be invisible, because indexing is gated on trust, and trust is gated on signals you earn off your own site.

Try it / break it

It's live and free: projectcalc.app

I'd genuinely love feedback from this crowd — on the calculators, the sketcher UX, or the indexing saga if you've fought it too. What finally tipped your new domains over the line? Drop it in the comments.

I built 73 free construction calculators in 11 days with Next.js. Here's what shipped, what broke, and what I learned about SEO for a brand-new domain

Brent — Thu, 07 May 2026 16:06:31 +0000

I built ProjectCalc — a free library of 73 calculators for construction, home improvement,
and DIY projects. No signup, no popups, no AI chatbot, runs entirely in your browser. Stack: Next.js 16 (App Router) +
TypeScript + vanilla CSS, deployed on Vercel.

Source: github.com/sabanite08/projectcalc

## Why

Every existing construction calculator on Google is buried under cookie banners, popup signups, AI chatbots, and ads.
The Reddit answer to "how much concrete do I need" is always a screenshot from someone else's calculator because the
original site is unusable.

So I built the version I wanted: dead simple, fast, no friction.

## What shipped

73 calculators across 6 categories:

Carpentry — beam span, header size, stair stringer, rafter length, floor joist span, snow load, plywood sheets, lumber cuts, framing
Electrical — voltage drop (NEC), conduit fill (Chapter 9), wire gauge (Table 310.16), panel load (NEC 220), circuit breaker (240.6), conduit bending, generator sizing
Plumbing — drain/vent/supply pipe sizing (IPC), trap size, pressure loss (Hazen-Williams), fixture units
HVAC — Manual J load, BTU sizing, duct CFM, refrigerant charge, static pressure, mini-split sizing
Home & DIY — concrete, drywall, paint, hardwood, roofing, tile, gravel, mulch, sod, pavers, fence, deck stain
Finance — mortgage, car payment, personal loan

Plus a visual room sketcher that draws your room as you type dimensions, then jumps
you into the matching calc with the numbers pre-filled. Handles L-shapes too.

Each calc shows the formula, worked example, common mistakes, and rules of thumb so you can sanity-check the result.
Code references documented (NEC, IPC, IRC, ACCA) where applicable.

## Stack

Next.js 16 with App Router, TypeScript, vanilla CSS (no Tailwind — wanted to keep the bundle tight)
Vercel for hosting + auto-deploy on push to main
Static generation for every calc page — they're all SSG'd, so first paint is sub-second
Single source of truth: lib/calculators.ts defines all 73 calcs as a typed array. The dynamic route /[slug]/page.tsx renders any of them. Adding a calc = adding one entry.

  // Calculator type — every calc is one entry in lib/calculators.ts
  export interface Calculator {
    slug: string;
    name: string;
    category: 'construction' | 'home' | 'finance' | 'utility';
    trade?: 'Carpentry' | 'Masonry & Siding' | 'Electrical' | 'Plumbing' | 'HVAC';
    desc: string;
    formula: string;
    metaTitle: string;
    metaDesc: string;
    seoIntro: string;
    howToUse?: string;
    workedExample?: string;
    commonMistakes?: string;
    rulesOfThumb?: string;
    inputs: CalcInput[];
    calc: (data: Record<string, string | number>) => CalcResult;
    // ...
  }

This was the highest-leverage decision in the whole codebase. New calculator = one new entry in the array, zero new
components.

## What worked

Static generation + small bundle. Every page prerenders to plain HTML at build time. Lighthouse scores 95+ across
the board. First Contentful Paint under 1s on a slow 3G simulation.

Schema.org structured data on every page. WebApplication + FAQPage on calc pages, BreadcrumbList everywhere,
ItemList on the homepage telling Google "this site has 73 calculators." Costs nothing, helps a lot for SERP features.

Companion blog posts. Every calculator has a 700-1,000 word companion blog post. Cross-linked to the calc and to
related calcs. This builds an internal link graph that Google can crawl efficiently.

Visual sketcher as a differentiator. Most calculator sites are forms. The room sketcher (live SVG drawing as you
type) is the one feature competitors don't have. Useful AND a unique selling point.

## What didn't work (yet)

This is the unsexy part nobody talks about when they launch.

1. Google AdSense rejected the site for "low value content" at day 8. The calc pages themselves were too thin —
just a form + short intro. Spent today rewriting every calc page to 800-1,200 words of contextual content (how to use
it, worked example, common mistakes, rules of thumb). Will reapply in 2-4 weeks.

2. impact.com Marketplace declined the site. Almost certainly traffic — was 8 days old. Direct Home Depot
affiliate also declined. Falling back to CJ Affiliate, ShareASale, FlexOffers as alternatives.

3. Google Search Console shows 94 of ~140 pages "Crawled - currently not indexed." Site age + zero backlinks =
Google being conservative. The fix is time (re-crawl after the prose expansion) plus earning a few backlinks.

4. Reddit's site-wide spam filter killed my launch post within minutes. Brand-new account + link post =
auto-removed. Need to build comment karma over a couple weeks before link posts clear.

## Lessons

For a new domain in any commercial niche, plan for 8-12 weeks of rejection-by-default before signals start coming through. Google, AdSense, affiliate networks, Reddit, HN — they all have new-site/new-account filters that exist because of the spammers who came before you.
Static + structured + cross-linked is table stakes for SEO. It's not a strategy, it's the floor. The strategy is the content depth on each page.
The single highest-leverage decision was the calculator schema. Adding a calc takes 10 minutes. If I had started with bespoke pages, adding the 50th calc would have been a 4-hour task.
Vulnerability beats hype. I'd rather post about getting denied by 3 affiliate networks than pretend I'm crushing it.

## Try it

projectcalc.app — click any calculator, no signup, runs in your browser.

Feedback I'm looking for:

Honest critique on whichever calc you click into first
Calcs you wish existed — if it's reasonable scope I'll add it
Anything broken on mobile (tested but limited devices)

Source on GitHub — issues and PRs welcome, especially formula corrections
with code citations.

What's the most over-engineered website you've ever needed for a 30-second math problem?