Largest Contentful Paint (LCP) measures when the largest visible image or text block finishes rendering in the viewport. It is one of Google's three Core Web Vitals and directly affects search ranking.

What are the LCP thresholds?

Google classifies LCP as Good if it is 2,500 ms or less, Needs Improvement if it is between 2,501 ms and 4,000 ms, and Poor if it exceeds 4,000 ms. These are the official 75th-percentile targets.

Should I use milliseconds or seconds?

This tool accepts both. If you type a value with a decimal point (e.g. 2.8) it is treated as seconds; whole numbers above 20 are treated as milliseconds. You can also explicitly select the unit from the dropdown.

What does the 75th percentile mean?

Google evaluates Core Web Vitals at the 75th percentile of real user sessions. That means 75 % of your visits must achieve the Good threshold for your site to pass. Optimizing only the median is not enough.

How do I measure my real LCP?

Use Chrome DevTools Performance panel, the Web Vitals Chrome extension, PageSpeed Insights (CrUX field data), or WebPageTest. Lighthouse gives a lab score; field data from CrUX reflects real users.

What are the most common causes of high LCP?

Slow server response times (TTFB), render-blocking JavaScript or CSS, unoptimized hero images (missing width/height, no lazy loading exemption, wrong format), and client-side rendering without SSR are the top culprits.

LCP Budget Calculator

Name: LCP Budget Calculator
Availability: InStock
Author: Nham Vu

Enter your measured or target LCP value and instantly see how it rates against Core Web Vitals thresholds — Good, Needs Improvement, or Poor.

Enter Your LCP Value

Quick presets:

Core Web Vitals Thresholds

Good ≤ 2,500 ms

Needs Improvement 2,501 – 4,000 ms

Poor > 4,000 ms

Enter an LCP value on the left to see your budget rating.

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Summary

Enter your measured or target LCP value and instantly see how it rates against Core Web Vitals thresholds — Good, Needs Improvement, or Poor.

How it works

Enter your current or measured LCP value in milliseconds or seconds.
The calculator normalizes your input and maps it to the three Core Web Vitals bands.
A color-coded result shows whether you are Good, Needs Improvement, or Poor.
The budget gap section tells you exactly how many milliseconds you need to save to reach the next threshold.
The percentile context panel explains what score to target for the 75th-percentile user.
Copy the summary to share your performance budget with your team.

Use cases

Set a measurable LCP performance budget before starting a project.
Evaluate Lighthouse or CrUX field data against Core Web Vitals thresholds.
Estimate how much render time you need to cut to reach a Good score.
Communicate performance targets clearly to designers and stakeholders.
Track LCP improvement week-over-week by comparing old vs. new values.
Quickly sanity-check a synthetic test result from WebPageTest or Lighthouse.
Prioritize optimization work by knowing exactly how far you are from each band.
Audit multiple pages at once by repeating the calculation for each URL.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu