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Core Web Vitals Budget Calculator

Check LCP, INP and CLS against Google’s good/needs-work/poor thresholds and see how much headroom you have before a metric slips into the next tier.

LCP (largest contentful paint)

INP (interaction to next paint)

CLS (cumulative layout shift)

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How it works

Good/Needs-work/Poor thresholds: LCP ≤2.5 s / ≤4.0 s · INP ≤200 ms / ≤500 ms · CLS ≤0.10 / ≤0.25

Core Web Vitals are the three user-experience metrics Google measures from real visitors: LCP for loading, INP for responsiveness and CLS for visual stability. Each has a Good cutoff and a Poor cutoff, and a page passes only when all three are Good at the 75th percentile of visits. This calculator classifies each metric and shows how much room is left before it crosses into the next-worse tier, so you know which one to defend first. Note that the field values Google uses come from the 75th percentile of real users, so lab numbers on a fast machine can look better than what actually gets reported.

Worked example

LCP 2.4 s is under the 2.5 s Good cutoff, with 0.1 s of headroom. INP 180 ms is under 200 ms, with 20 ms to spare. CLS 0.08 is under 0.10. All three are Good, so the page passes — but LCP and INP have little margin, so a heavier hero image or a slow script could tip either one.

Sources: Google web.dev — Core Web Vitals

Frequently asked questions

Why does one bad metric fail the whole page?

Google’s Core Web Vitals assessment is pass-only-if-all-pass: a URL is judged good only when LCP, INP and CLS are all in the Good band. A single Poor metric fails the assessment, so it usually pays to fix your worst vital before optimising a metric that already passes.

What replaced FID?

INP (Interaction to Next Paint) replaced FID (First Input Delay) as the responsiveness vital in March 2024. INP measures the latency of all interactions across the visit, not just the first, so it is a stricter, more representative test of how snappy the page feels.

Lab data or field data?

Search uses field data — real Chrome users in the CrUX dataset at the 75th percentile. Lab tools like Lighthouse are great for debugging but can differ from the field, so confirm improvements in a field source such as the Search Console Core Web Vitals report before assuming a fix landed.

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This calculator is for educational purposes. Double-check important results before acting on them.