The verdict in three sentences
Reaching LCP under 2.5 s and INP under 200 ms on a B2B site in Miami runs through a performance audit of 1,200 to 2,800 EUR then a Next.js/SSR front-end rebuild of 12,000 to 30,000 EUR. The return shows in conversion: +8 to 15% leads from faster pages. Plan 6 to 10 weeks, a CDN at 30-120 EUR/month and contractual performance clauses to secure the result.
The Core Web Vitals thresholds to target in 2026
Google scores three key metrics. Beating them improves ranking and user experience, two direct levers of B2B conversion.
| Metric | Good | Needs work | Poor |
|---|---|---|---|
| LCP (loading) | < 2.5 s | 2.5 - 4 s | > 4 s |
| INP (interactivity) | < 200 ms | 200 - 500 ms | > 500 ms |
| CLS (stability) | < 0.1 | 0.1 - 0.25 | > 0.25 |
| TTFB (server) | < 800 ms | 800 - 1,800 ms | > 1,800 ms |
| Page weight | < 1.5 MB | 1.5 - 3 MB | > 3 MB |
A slow B2B site loses leads before the contact page: every second of LCP beyond 2.5 s can cut conversion by several points.
The detailed performance quote
| Line item | 2026 range | Detail |
|---|---|---|
| Performance audit | 1,200 - 2,800 EUR | Lighthouse, profiling, action plan |
| Next.js/SSR front rebuild | 12,000 - 30,000 EUR | SSR/ISR, code splitting |
| WebP/AVIF image optimization | Included | Compression, lazy-loading |
| CDN | 30 - 120 EUR/month | Edge cache, lower latency |
| Continuous CWV monitoring | 40 - 150 EUR/month | Regression alerts |
| Delivery timeline | 6 - 10 weeks | Front rebuild only |
The performance clauses to put in the contract
A serious performance quote commits the agency to measurable results, not just deliverables.
| Clause | Typical commitment | Verification |
|---|---|---|
| Mobile Lighthouse score | >= 90 | Acceptance audit |
| Field LCP (CrUX) | < 2.5 s on 75% | Search Console |
| Field INP | < 200 ms on 75% | Search Console |
| Home page weight | < 1.5 MB | Acceptance |
| Regression fix | Within 5 days | SLA |
Mini case study
Thomas, IT director of a 60-person digital services SMB in Miami, commissions a front rebuild at 21,000 EUR plus a 2,000 EUR audit. His LCP drops from 3.8 s to 2.1 s and INP from 420 ms to 160 ms. The site converts 1,200 visitors/month: with a +11% conversion gain, from 2.4% to 2.66%, he gets about 3 extra leads per month. At a 15,000 EUR average contract and a 14% close rate, that is nearly 6,300 EUR of additional monthly revenue: the rebuild pays back in a little over three months.
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FAQ
Why do Core Web Vitals matter for B2B?
Because they influence Google ranking and experience: an LCP under 2.5 s reduces abandonment and lifts leads by 8 to 15%. In B2B every lead is valuable, so the gain is quickly recouped.
Do I have to move to Next.js?
Not always, but Next.js SSR/ISR greatly eases hitting the thresholds. A front rebuild costs 12,000 to 30,000 EUR depending on complexity and number of templates.
How long to see SEO impact?
Technical gains are immediate on Lighthouse, but field data (CrUX) updates over 28 days. The SEO effect shows over 2 to 4 months after launch.
Is image optimization enough?
Rarely alone. WebP/AVIF cuts weight, but INP and TTFB depend on JavaScript and server. A holistic front + hosting approach is needed.
Can a score be guaranteed by contract?
Yes: you contract a Lighthouse score >= 90 and field thresholds, with a 5-day fix SLA on regressions. Demand these clauses in the quote.
Let's scope your project. Performance audit plus Next.js front rebuild, target LCP < 2.5 s and INP < 200 ms, indicative budget 12,000 to 30,000 EUR: tell us your templates and volume. 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.
