Core Web Vitals Budget Calculator

Google defines three tiers for each metric. LCP (Largest Contentful Paint): Good ≤ 2500ms, Needs Improvement 2500–4000ms, Poor > 4000ms. INP (Interaction to Next Paint): Good ≤ 200ms, Needs Improvement 200–500ms, Poor > 500ms. CLS (Cumulative Layout Shift): Good ≤ 0.1, Needs Improvement 0.1–0.25, Poor > 0.25. All three must be in the 'Good' range to pass the Core Web Vitals assessment.

LCP (Largest Contentful Paint) measures how long it takes for the largest visible element (hero image, headline, video thumbnail) to fully render. To improve it: 1) Preload the LCP image with <link rel='preload'>. 2) Use a CDN to reduce server response time. 3) Avoid lazy-loading the LCP element. 4) Use modern image formats (WebP/AVIF) with appropriate sizes. 5) Inline critical CSS to eliminate render-blocking. Target: < 2500ms for at least 75% of page loads.

INP (Interaction to Next Paint) replaced FID as an official Core Web Vital in March 2024. Unlike FID (which measured only the input delay of the first interaction), INP captures the full latency of all interactions — tap, click, or key press — and reports the worst one. To improve INP: break up long tasks with setTimeout/scheduler.yield, reduce JavaScript execution time, use web workers for heavy computation, and defer non-critical scripts.

CLS (Cumulative Layout Shift) measures how much page content unexpectedly moves during load. A score of 0 means no shifting; higher is worse. Common causes: images/videos without explicit width and height attributes, ads or embeds injecting content above existing text, web fonts causing FOIT/FOUT reflow, and dynamically inserted banners. Fix: always declare image dimensions, use CSS aspect-ratio, and load fonts with font-display: optional.

Google uses Core Web Vitals as part of its 'Page Experience' ranking signal. The signal is based on field data from the Chrome User Experience Report (CrUX), which aggregates real user measurements. A page passes Core Web Vitals if at least 75% of visits achieve 'Good' scores on all three metrics. Failing doesn't cause a ranking penalty per se, but passing can give a small positive signal when other ranking factors are equal.