The verdict in three sentences
A London B2B site with Core Web Vitals in the red loses ranking and up to 15% of mobile conversions. In 2026, serious optimization costs 3,500 to 9,000 EUR on top of the audit (1,200 to 3,000 EUR), to bring LCP under 2.5s, INP under 200ms and CLS under 0.1. The payoff is measurable within 4 to 8 weeks: better positioning, lower bounce, a smoother conversion funnel.
What a Core Web Vitals optimization covers
The three official metrics weigh differently on experience. LCP (Largest Contentful Paint) measures how fast the largest visible element renders, INP (Interaction to Next Paint) responsiveness to clicks, and CLS (Cumulative Layout Shift) visual stability. A single red metric is enough to fail Google's "good" assessment.
A typical project combines image optimization (WebP/AVIF, lazy loading), reducing blocking JavaScript, caching and CDN, deferring third-party scripts and fonts, and reworking critical rendering. Here are the 2026 workstreams and their typical gains.
| Workstream | 2026 cost (EUR) | Target metric | Typical gain |
|---|---|---|---|
| Full audit + prioritization | 1,200 - 3,000 | All three | Costed roadmap |
| WebP/AVIF images + lazy loading | 800 - 2,000 | LCP | -30 to -50% weight |
| JS reduction + code splitting | 1,500 - 4,000 | INP | -100 to -300 ms |
| Space reservation (dimensions) | 600 - 1,800 | CLS | CLS < 0.1 |
| CDN + server cache | 700 - 2,200 | LCP | -0.5 to -1.5 s |
| Font optimization (font-display) | 400 - 1,200 | LCP/CLS | -200 to -600 ms |
2026 pricing and timelines in London
Price depends on the CMS (WordPress, Next.js, Shopify), page volume and starting state. A 20-40 page B2B brochure site is handled faster than one with e-commerce or a customer portal. The CDN remains a modest monthly subscription relative to the gains.
| Service | 2026 range (EUR) | Timeline |
|---|---|---|
| Performance audit only | 1,200 - 3,000 | 1 week |
| Brochure site optimization (20-40 pages) | 3,500 - 6,000 | 3 - 4 weeks |
| Complex / e-commerce optimization | 6,000 - 9,000 | 4 - 6 weeks |
| Managed CDN + WAF | 30 - 150 /month | Ongoing |
| CWV monitoring (RUM) | 40 - 120 /month | Ongoing |
| Quarterly perf retainer | 1,500 - 3,500 | Per quarter |
Mini case study
James, e-marketing lead at an industrial SME in London, runs a 35-page brochure site with LCP at 4.1s and INP at 340ms. He invests 5,200 EUR in optimization (images, JS, CDN) plus 60 EUR/month for the CDN. LCP drops to 2.2s, INP to 170ms. Across 3,200 monthly sessions converting at 2.1% with a 1,400 EUR average B2B order, a +9% conversion gain represents roughly 8,100 EUR of extra monthly revenue. The investment pays back in under three weeks, before counting organic ranking gains.
FAQ
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How much does a standalone Core Web Vitals audit cost in 2026?
Between 1,200 and 3,000 EUR depending on depth (CrUX field data + Lighthouse lab, impact-based prioritization). The audit delivers a costed roadmap, not just a score.
How long until results show on Google?
Field data updates on a rolling 28-day window. Expect 4 to 8 weeks for the improvement to reflect in Search Console and ranking.
Is a CDN really essential?
For a B2B site with national or international traffic, yes: a 30-150 EUR/month CDN cuts LCP by 0.5 to 1.5s by bringing files closer to the user. It's often the best cost/gain ratio.
Can a heavy WordPress site be optimized without a full rebuild?
Yes in 70% of cases: caching, plugin pruning, images and JS are enough to go green for 3,500 to 6,000 EUR. Beyond that, a headless migration becomes worthwhile.
What ROI should I realistically expect?
A 2026 sector study puts the gain at +5 to 15% conversions depending on starting state, plus a ranking effect. On a B2B funnel, that often exceeds 10,000 EUR/year in additional revenue.
Let's scope your project. Send us the URL, your CMS and current scores: we quote the audit and optimization with a contractual LCP/INP/CLS target and an indicative budget. 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.
