The 7 Findings That Define Page Speed in 2026
The seven defining findings: (1) every 1s of LCP delay drops conversion rate by 11.4% on the median site; (2) sites at sub-1.5s LCP convert at 2.7x the rate of sites at >6s LCP; (3) INP > 200ms reduces CR by 23%, a stronger commercial signal than FID ever was; (4) CLS >0.25 doubles form abandonment from 18.7% to 38.4%; (5) mobile-poor sites lose 52% of CR at >4s LCP vs 40% on desktop; (6) median speed-project payback is 4.7 months; (7) image format conversion delivers the single largest LCP win for most templates.
The "speed equals revenue" claim has been canon for a decade — but most published numbers trace to a 2017 Akamai study and a 2018 Google "Milliseconds Earn Millions" paper that never reproduced. We rebuilt the analysis with current-cycle data: 2.4 million sessions, GA4 + CrUX paired, segmented by sector, device, and conversion type.
LCP vs Conversion Rate: The Revenue Curve
Sites achieving sub-1.5s LCP convert at 5.84% median, vs 2.18% for sites at >6s — a 2.7x uplift. The steepest drop sits between 2.5s and 4s, where most non-optimised sites live. Google's official "Good" threshold of 2.5s is the floor, not the ceiling: the additional CR lift from going from 2.5s to 1.5s is 17%.
| LCP bucket | Median CR | vs <1.5s baseline | Sample sessions |
|---|---|---|---|
| <1.5s | 5.84% | Baseline | 284,000 |
| 1.5-2.5s (Good) | 4.97% | -14.9% | 642,000 |
| 2.5-4.0s (Needs work) | 4.12% | -29.5% | 718,000 |
| 4.0-6.0s | 3.21% | -45.0% | 421,000 |
| >6.0s (Poor) | 2.18% | -62.7% | 335,000 |
Source: Visionary 240-Site Performance Study 2026.
Median conversion rate by LCP bucket. Source: Visionary 2026.
Fastest LCP wins in 2026: (1) Convert JPEG/PNG to WebP/AVIF on hero images; (2) self-host critical fonts and subset to used glyphs; (3) defer non-critical JS via dynamic import; (4) preload the LCP image with fetchpriority="high"; (5) replace third-party tag managers with server-side equivalents.
INP vs Conversion Rate
INP replaced FID as the official responsiveness metric in March 2024. The commercial signal is stronger: sites with INP >500ms convert at 58% lower rates than sites with INP <100ms, and AOV drops £13 per order on the worst-INP cohort. The dominant INP killer in 2026: third-party tags injected via Google Tag Manager.
| INP bucket | Median CR | vs <100ms | AOV (£) |
|---|---|---|---|
| <100ms (Excellent) | 5.62% | Baseline | 84.40 |
| 100-200ms (Good) | 4.81% | -14.4% | 82.10 |
| 200-500ms (Needs work) | 3.71% | -34.0% | 78.20 |
| >500ms (Poor) | 2.34% | -58.4% | 71.40 |
Source: Visionary 2026.
CLS vs Conversion Rate
CLS is the most underrated commercial signal. Form abandonment doubles between CLS <0.05 and CLS >0.25. Layout shifts during form entry cause mis-clicks, lost focus and frustrated abandonment — a measurable revenue leak that most teams ignore because CLS rarely fails Google's automated checks at audit time.
| CLS bucket | Median CR | Cart-add rate | Form-abandon rate |
|---|---|---|---|
| <0.05 (Excellent) | 4.92% | 12.4% | 18.7% |
| 0.05-0.10 (Good) | 4.41% | 11.2% | 21.4% |
| 0.10-0.25 (Needs work) | 3.62% | 9.4% | 27.8% |
| >0.25 (Poor) | 2.41% | 7.1% | 38.4% |
Source: Visionary 2026.
Mobile vs Desktop: Where the Revenue Hides
Mobile carries 64% of e-commerce sessions but only 41% of revenue. The CR gap closes dramatically with speed: mobile sub-2.5s sites hit 3.81% CR vs 2.94% for 2.5-4s and 1.84% for >4s. Mobile speed is the single largest revenue lever in the 2026 dataset.
| Device + LCP | Median CR | Bounce | AOV (£) |
|---|---|---|---|
| Mobile <2.5s | 3.81% | 38.4% | 72.10 |
| Mobile 2.5-4s | 2.94% | 47.2% | 68.40 |
| Mobile >4s | 1.84% | 61.7% | 62.10 |
| Desktop <2.5s | 6.42% | 21.4% | 94.80 |
| Desktop 2.5-4s | 5.21% | 27.8% | 91.20 |
| Desktop >4s | 3.84% | 38.6% | 84.40 |
Source: Visionary 2026.
Speed Impact by Sector
| Sector | Median LCP | CR at Good LCP | CR at Poor LCP | Revenue / 100ms saved |
|---|---|---|---|---|
| E-commerce / DTC | 2.84s | 4.21% | 1.94% | £0.84 |
| B2B SaaS | 2.42s | 5.84% | 2.81% | £2.14 |
| Financial services | 2.61s | 4.41% | 2.04% | £3.84 |
| Travel | 3.42s | 3.71% | 1.42% | £1.94 |
| News / publishing | 3.21s | 2.84% | 1.21% | £0.21 |
| Education | 2.74s | 4.84% | 2.41% | £0.94 |
| Local services | 3.04s | 5.21% | 2.71% | £1.41 |
| B2B services | 2.51s | 4.94% | 2.21% | £1.84 |
Source: Visionary 240-Account Performance Study 2026.
Revenue Per Millisecond Saved
Translating the speed curve to revenue, the median 240-account site gains £0.84 per session per 100ms LCP improvement. At 50,000 monthly sessions that's £504/month per 100ms; at 500,000 sessions, £5,040/month. The most leveraged speed wins are the cheap-to-fix ones — image format, font subsetting, JS code-splitting.
| Speed improvement | CR lift (median) | Revenue lift (median site) |
|---|---|---|
| LCP -100ms | +1.1% | +£0.84 per session |
| LCP -500ms | +5.4% | +£4.21 per session |
| LCP -1s | +11.4% | +£8.94 per session |
| INP -100ms | +2.8% | +£2.41 per session |
| CLS -0.10 | +8.7% | +£6.84 per session |
Source: Visionary 2026.
Bounce Rate & Time-on-Page by LCP
| LCP bucket | Bounce rate | Pages / session | Time on page |
|---|---|---|---|
| <1.5s | 21.4% | 4.84 | 2m 41s |
| 1.5-2.5s | 27.8% | 4.21 | 2m 18s |
| 2.5-4s | 38.6% | 3.41 | 1m 47s |
| >4s | 54.2% | 2.41 | 1m 12s |
Bounce more than doubles between sub-1.5s LCP and >4s LCP. Source: Visionary 2026.
Page Speed Score Card — Estimate Your Lift
Enter your current Core Web Vitals and traffic. We estimate the conversion-rate and revenue lift available if you reach Excellent.
Speed Index
64/100
LCP 70 · INP 63 · CLS 60
CR lift if optimised
+0.0%
Modelled lift to median CR after reaching Excellent CWV.
Monthly revenue lift
£0
Indicative — confirm with paired GA4 + CrUX data.
Indicative model. Pair with a full performance audit for precise figures.
Methodology
Source 1: Visionary 240-Account Performance Study 2026. 2.4M sessions across 240 client accounts. GA4 paired with CrUX field data via the CrUX BigQuery export. Conversion rate measured on completed-purchase / qualified-lead events. Segmented by device, sector and traffic source. Q1 2026.
Source 2: Visionary Mass CRO Practitioner Survey 2026 (n=900). Used to validate practitioner consensus on payback timeframes, prioritisation and tooling.
Limitations: speed is one variable among many; correlation does not imply causation in every case; sector-specific variation is substantial; sites with very low traffic may show wider confidence intervals. For media enquiries: press@visionary-marketing.co.uk.
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