The verdict in three sentences
Core Web Vitals are not a developer's whim: they weigh on search rankings and above all on B2B conversion rates. An audit at 1,200-3,500 EUR pinpoints the levers, an optimisation sprint at 2,800-7,000 EUR fixes them in 5 to 12 days. The observed gains — +8 to +15 % conversion, -20 % bounce — often exceed the audit cost within the first quarter.
The three metrics and their 2026 thresholds
Google measures three signals that determine whether a page is rated "good", "needs improvement" or "poor". A B2B site must aim for green on all three at the 75th percentile of its mobile visitors.
| Metric | 2026 target | Needs improvement | Poor |
|---|---|---|---|
| LCP (loading) | < 2.5 s | 2.5 to 4 s | > 4 s |
| INP (interactivity) | < 200 ms | 200 to 500 ms | > 500 ms |
| CLS (visual stability) | < 0.1 | 0.1 to 0.25 | > 0.25 |
| TTFB (server) | < 800 ms | 800 ms to 1.8 s | > 1.8 s |
Cost per technical lever
Each optimisation has a different cost and impact. Prioritisation follows the effort/impact ratio, not alphabetical order.
| Technical lever | Indicative cost | Estimated LCP/INP gain | Effort |
|---|---|---|---|
| WebP/AVIF image compression | 400-900 EUR | -0.4 to -1.2 s LCP | Low |
| Lazy-loading images and iframes | 300-700 EUR | -0.3 to -0.8 s LCP | Low |
| Caching + CDN | 600-1,500 EUR | -0.5 to -1.5 s TTFB | Medium |
| Reducing third-party JavaScript | 800-2,000 EUR | -80 to -250 ms INP | High |
| Font preloading | 250-500 EUR | -0.2 s LCP, CLS stabilised | Low |
| Rendering rebuild (SSR/static) | 2,500-6,000 EUR | -1 to -2.5 s LCP | Very high |
Speed and conversion correlation
On a B2B site, every second gained on LCP mechanically translates into conversion points. Here are 2026 orders of magnitude observed on lead-generation sites.
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| Measured LCP | Form conversion rate | Bounce rate |
|---|---|---|
| > 4 s | 1.4 % | 62 % |
| 3 to 4 s | 2.1 % | 54 % |
| 2.5 to 3 s | 2.8 % | 47 % |
| < 2.5 s | 3.6 % | 41 % |
Mini case study
Sabine, CIO of a mid-market B2B logistics firm in Amsterdam, orders a CWV audit at 2,400 EUR. The site shows an LCP of 3.8 s and a 1.9 % conversion rate. The optimisation sprint (WebP, lazy-loading, CDN) costs 4,200 EUR and brings LCP down to 2.3 s. Conversion climbs to 3.1 %, a relative +63 %. On 30,000 visitors/month and a lead value of 900 EUR, that means about 360 extra leads per year, for a total investment of 6,600 EUR recovered in under two months.
FAQ
Is a CWV audit useful if I'm rebuilding soon? Yes, it quantifies the gap and frames the rebuild specification. Without a baseline measurement, you cannot prove the gain afterwards.
What's the difference between lab and field data? Lab (Lighthouse) is reproducible but theoretical; field (CrUX, Search Console) reflects your real visitors. Google uses field data for ranking.
How long to see the SEO effect? Improved INP and LCP surface in Search Console within 28 days, but the effect on positions smooths out over 6 to 10 weeks.
Is a CDN essential? For an international B2B site or one with many images, yes: it decisively cuts TTFB. For a light local site, caching sometimes suffices.
Can everything be optimised without a rebuild? Often 70 to 80 % of gains are achievable on the existing site. The remaining 20 % sometimes require a rendering change (SSR or static generation).
Let's scope your project. Send us the URL to audit and your monthly traffic: we deliver a costed CWV report with an effort/impact prioritisation plan. 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.
