Latency and conversion sandbox: the model behind the homepage slider

The latency slider on the homepage is one of the most-read parts of this site, so it should be honest about what it is: a static model that runs entirely in the browser, with no data collection, no account and no server round trip.

#What the model does

The slider takes one input — Largest Contentful Paint in seconds, from 0.6 to 4.5 — and produces four outputs. Every output is a linear function of that input, which makes the model easy to audit and impossible to hide behind.

#The formulas

Projected conversion is a declining line across the slider range:

conversion(lcp) = max(1.1, 5.5 - (lcp × 0.95))

Bounce probability rises with the same input:

bounce(lcp) = min(68, 4.5 + (lcp × 11.2))

Annual impact is expressed against an explicit baseline, so the constant is visible:

annualImpact(lcp) = (conversion(lcp) - 3.2) × $85,000

The perceived performance score is a compressed, 100-point scale:

score(lcp) = max(18, round(105 - (lcp × 22)))

#What it is not

It is not a prediction for your traffic, and it does not come from a study of your users. The constants are chosen so the curve is monotone and legible at a glance. If you want a real model, run a real experiment on your own funnel — that is the only version of this number worth acting on.

#Why publish the formulas

A slider that shows impressive-looking numbers with no explanation is a trust problem waiting to happen. Publishing the arithmetic means you can check it, argue with it, and reuse it. Everything on this page runs in your browser: no cookies, no beacons, no requests.