The verdict in three sentences
When a B2B website fails INP and mobile LCP, the right first spend is an audit at EUR 1,200 to 3,000 (USD 1,300 to 3,300), not a redesign. In most cases targeted fixes at EUR 3,000 to 12,000 (USD 3,300 to 13,000) are enough to reach LCP under 2.5 s and INP under 200 ms within 3 to 6 weeks. A full rebuild (EUR 15,000 to 40,000, USD 16,000 to 43,000) is only justified when the CMS, theme or architecture make those thresholds unreachable.
What Core Web Vitals actually measure in 2026
Google evaluates three metrics on real Chrome user data (the CrUX report), at the 75th percentile, over a rolling 28 days. An industrial B2B site often has modest mobile traffic, which makes field data noisy: cross-check CrUX, Search Console and your own real-user monitoring (RUM) before drawing conclusions.
| Metric | Good | Needs improvement | Poor | Common cause on a B2B site |
|---|---|---|---|---|
| LCP (main content render) | < 2.5 s | 2.5 to 4 s | > 4 s | 1.5 MB hero image, render-blocking font |
| INP (responsiveness) | < 200 ms | 200 to 500 ms | > 500 ms | Chat scripts, marketing tags, page builder |
| CLS (visual stability) | < 0.1 | 0.1 to 0.25 | > 0.25 | Cookie banner, images without dimensions |
| TTFB (diagnostic metric) | < 0.8 s | 0.8 to 1.8 s | > 1.8 s | Shared hosting, no caching |
| Mobile JavaScript weight | < 300 KB | 300 to 800 KB | > 800 KB | Multi-purpose theme, stacked plugins |
INP, which replaced FID in 2024, has become the number one weakness of B2B sites: product configurators, catalogue filters and chat widgets block the browser's main thread at the exact moment the user clicks.
Targeted fixes or rebuild: the decision grid
The audit should produce a prioritised list, priced per fix, with the expected gain on each metric. The decision depends mainly on the technical foundation.
| Technical foundation | Targeted fixes | Realistic gain | Rebuild recommended if |
|---|---|---|---|
| WordPress with a lightweight theme | EUR 3,000 to 6,000 | LCP under 2.5 s achievable | More than 40 active plugins |
| WordPress with a page builder | EUR 5,000 to 10,000 | INP often stuck around 250 ms | Builder loads over 500 KB of JS |
| Proprietary CMS or legacy Drupal | EUR 6,000 to 12,000 | Depends on code access | Unsupported version |
| Next.js or modern framework | EUR 3,000 to 8,000 | Thresholds reachable everywhere | Rarely |
| No-code platform site | EUR 1,500 to 4,000 | Capped by the platform | INP > 300 ms after fixes |
| Full rebuild | EUR 15,000 to 40,000 | Thresholds written into the spec | When 2 criteria above combine |
The most profitable fixes are almost always the same: images served as AVIF or WebP with explicit dimensions, preloading the hero image, self-hosted fonts, deferring marketing scripts through server-side tag management, CDN caching and removing unused plugins.
Measure business gain, not just the score
A Lighthouse score of 95 is not a commercial goal. What matters is mobile conversion rate (quote request, datasheet download, contact) before and after. On our 2025 and 2026 projects, the measured gain sits between 10 and 20% in mobile conversion at constant traffic. Allow 28 days after release for CrUX data to settle.
Mini case study
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Emma, marketing manager at a 120-employee industrial manufacturer in Manchester, sees her WordPress site fail with a mobile LCP of 4.6 s and an INP of 410 ms. The site gets 9,000 mobile visits a month and converts at 0.8%, or 72 requests. The EUR 2,000 audit identifies 14 fixes, priced at EUR 7,500. After 5 weeks, LCP drops to 2.1 s and INP to 180 ms. Mobile conversion rises to 0.95%, or 85 requests: 13 more a month. With a 10% win rate and an average deal of EUR 18,000, that is about 1.3 extra deals a month. The EUR 9,500 invested pays back with the first order, whereas a EUR 30,000 rebuild would have taken 4 more months.
FAQ
Do Core Web Vitals really affect rankings?
They are part of the page experience signals, with real but secondary weight compared with content relevance. Their main effect is commercial: an LCP dropping from 4 s to 2 s cuts mobile bounce rate by 15 to 30% according to industry studies.
How much does a serious Core Web Vitals audit cost?
Between EUR 1,200 and 3,000 (USD 1,300 to 3,300) for a B2B site of 20 to 200 pages. It should include CrUX analysis, performance traces on 5 to 10 templates and a priced list of fixes.
Why is my Lighthouse score good while Search Console is red?
Lighthouse measures in the lab, Search Console on real visitors. A desktop score of 90 can hide a 400 ms INP on a mid-range smartphone.
How long before Google sees the improvements?
CrUX data covers a rolling 28 days. Allow 4 to 6 weeks after release for Search Console to turn green.
Is monitoring needed after the fixes?
Yes, every new plugin or marketing tag can degrade INP. Monthly monitoring costs EUR 150 to 400 and includes an alert as soon as a metric crosses the threshold again.
Let's scope your project. Send us your site URL and CMS: we will estimate the audit, the fix budget and the time needed to turn green. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
