Single-Page Passive Income: The Inches-to-CM Case

Inches-to-cm.com proves that extremely simple sites can produce years of passive income. Registered in 2013, the three-page site generates roughly $1,000 monthly from a function that takes one line of code to implement.

The Product

The site converts inches to centimeters. That’s it. A conversion formula, a lookup table of common conversions, and related length comparisons. Three pages covering one tiny need.

The equivalent JavaScript is trivial. Yet dedicated search demand for “inches to cm” exists because people want instant answers without doing mental math.

Traffic and Revenue

Monthly visits range from 240,000 to 380,000. Four ad placements generate revenue on each page view. At conservative $1-2 eCPM for the primarily UK/European traffic, monthly revenue easily exceeds $1,000.

Over a decade of consistent traffic, estimated cumulative revenue approaches $100,000 or more. For a site requiring virtually no maintenance after initial creation.

Early Mover Advantage

The site launched when competition was minimal. A decade of backlink accumulation and domain authority makes displacement difficult even as Google now shows conversion answers directly in search results.

Newer competitors face Google’s direct answers capturing many clicks. The established site retains enough residual traffic and authority to remain profitable despite changed conditions.

The Economics of Simple

Development cost was minimal: a single page of HTML with basic styling. Hosting costs are negligible. No customer support, no feature development, no content updates needed.

Every dollar of revenue is nearly pure profit after hosting fees. The return on investment ratio is extraordinary because the investment was negligible.

Replication Challenges

The opportunity to replicate this specific approach has diminished. Google’s featured answers capture search intent for simple conversions. But the principle remains: micro-needs served early with minimal complexity can produce disproportionate long-term returns.