Site Speed → Revenue Calculator

 

Turn Site Speed Into Revenue: The Definitive Guide to Core Web Vitals ROI

Slow pages don’t just annoy users—they cost real money. This guide explains how improving Core Web Vitals (CWV) translates into higher conversion, better engagement, and more revenue. Use the calculator above to model your own numbers, then follow the playbook below to capture the upside.

What are Core Web Vitals (and why they matter for revenue)?

Core Web Vitals are Google’s user‑centric performance metrics:

  • LCP (Largest Contentful Paint): how quickly the main content appears (target ≤ 2.5s).

  • INP (Interaction to Next Paint): responsiveness to user input (target ≤ 200ms).

  • CLS (Cumulative Layout Shift): visual stability (target ≤ 0.1).

When these improve, users bounce less, browse more, and buy more. On ecommerce, this surfaces as higher conversion rate and higher revenue per session. For publishers and affiliates, it shows up as higher RPM/EPC thanks to deeper engagement and more ad or partner clicks.

How the calculator converts speed into money

The calculator estimates revenue uplift using a simple, transparent relationship between LCP improvement and business metrics:

  • For ecommerce: conversion rate change per 100ms faster LCP

  • For content/affiliate: RPM/EPC change per 100ms faster LCP

You can set the “elasticity” yourself and switch between Conservative / Expected / Aggressive scenarios to see a band of outcomes. Then it computes:

  • Monthly revenue uplift

  • Payback period (months) based on your one‑off optimization cost

  • 12‑month ROI (%)

The model in plain English

  1. Measure your current LCP and set a realistic target (e.g., 3.5s → 2.0s).

  2. Choose an elasticity (e.g., 0.35% conversion lift per 100ms faster LCP).

  3. The calculator projects the new conversion (or RPM) and multiplies by your traffic and AOV (or sessions × RPM) to estimate monthly uplift.

This is a directional forecast, not a guarantee—but it’s a powerful way to prioritize performance work by expected business impact.

Quick wins vs. deep fixes: where the revenue usually hides

  • Image weight: Serve responsive images (srcset), compress aggressively (AVIF/WebP), lazy‑load offscreen images, set width/height to avoid CLS.

  • JavaScript diet: Remove dead code, split bundles, defer non‑critical scripts, delay 3rd‑party tags, prefer native browser features over heavy libraries.

  • Critical rendering path: Inline critical CSS, preload the hero image and key fonts, defer everything else.

  • Server & caching: Use CDN caching, HTTP/2 or HTTP/3, efficient SSR, and keep TTFB low with edge caching.

  • Fonts: Use font-display: swap, subset fonts, and avoid layout jumps from late font swaps.

  • 3rd‑party governance: Audit marketing pixels and chat widgets; load them after interaction or conditionally.

Step‑by‑step: How to use the calculator (and what to do with the result)

  1. Pick your model (Ecommerce or Affiliate/Content).

  2. Enter current business metrics: monthly sessions, CR & AOV (or RPM).

  3. Enter your current and target LCP (add INP/CLS for context).

  4. Choose an elasticity (start with the default, then test conservative/aggressive).

  5. Review monthly uplift, payback, and 12‑month ROI.

  6. Turn the output into a plan:

    • If payback is < 3 months, prioritize performance immediately.

    • If payback is 3–6 months, bundle speed work with a planned redesign or platform change.

    • If payback is > 6 months, aim for smaller, surgical fixes (image pipeline, 3rd‑party trims) to pull ROI forward.

Example scenarios (illustrative)

  • Ecommerce store: 100k sessions/month, CR 2.0%, AOV €60, LCP 3.5s → 2.0s, elasticity 0.35%/100ms, dev cost €18k.
    → Expected monthly uplift ≈ €6,300, payback ≈ 2.9 months, 12‑month ROI well above 200%.

  • Affiliate site: 500k sessions/month, RPM €18, LCP 4.0s → 2.5s, elasticity 0.25%/100ms, dev cost €12k.
    → Expected monthly uplift in the low €000s range, typically sub‑3‑month payback.

(Your numbers will differ—use the calculator to model your own.)

Prioritization framework: 20/80 performance roadmap

  1. Measure: PageSpeed Insights, Lighthouse, and field data from CrUX or your RUM tool.

  2. Locate the bottleneck: Is it network (TTFB), render‑blocking (CSS/JS), or bytes (images/fonts)?

  3. Estimate business impact: Use this calculator to rank issues by € uplift and payback.

  4. Implement: Ship the smallest change that drops LCP/INP meaningfully (e.g., hero image preload + JS defer).

  5. Verify: Re‑measure in field data—lab wins must show up in real user metrics.

  6. Institutionalize: Add CWV budgets to CI, tag governance, and a quarterly “speed tax” to keep gains.

Common mistakes that tank Core Web Vitals

  • Shipping a marketing tag salad that blocks the main thread.

  • Over‑hydrated JS for static pages; use partial or islands hydration.

  • Hero media without preload hints.

  • Fancy web fonts with no fallbacks and no subsetting.

  • Treating CWV as a one‑off project instead of an ongoing product hygiene practice.

How Bubble Marble helps (and what “done” looks like)

  • Audit to actions: We map lab findings to field impact and prioritize by payback.

  • Fix pipeline: From image automation to JS code‑splitting and 3rd‑party governance.

  • Guardrails: Budgets, dashboards, and weekly deltas so regressions don’t creep back.

  • Business reporting: Tie performance to revenue so wins are visible to leadership.

Want a tailored plan? Get a free performance review →

FAQs

Is improving Core Web Vitals also an SEO ranking factor?
Performance is one of many signals. Faster pages can help, but the primary win is conversion/engagement uplift, which is measurable right away.

What elasticity should I use?
Start with 0.35% per 100ms for ecommerce as a pragmatic “expected” value. If your audience is mobile‑heavy, test a higher value; if desktop‑heavy with long consideration cycles, test lower.

Should I optimize LCP, INP, or CLS first?
Start with LCP for the fastest commercial payoff, then tackle INP (JS main‑thread issues) and CLS (stability) for compounding gains.

How do I get accurate LCP numbers?
Use field data (CrUX, RUM) to see real‑user performance. Lab tools are great for debugging, but decisions should be grounded in field metrics.

Will a redesign fix everything?
Not by itself. Most gains come from assets, critical path, and 3rd‑party control. Redesigns can help if they also simplify the tech.

How soon will I see results?
Once the changes ship and cache/CDN propagate, impact can be immediate. Field datasets (like CrUX) update on a delay; use your analytics to monitor conversion and revenue right away.

Implementation checklist (copy & paste)

  • Measure current LCP/INP/CLS in field data

  • Identify the top 5 blocking issues (images, CSS, JS, 3rd parties, TTFB)

  • Model ROI in the calculator for 3 scenarios

  • Prioritize tasks by payback < 3 months

  • Ship fixes behind flags; A/B test where practical

  • Add budgets and dashboards; review weekly

Conclusion

Performance is product. By turning Core Web Vitals into clear financial outcomes, you can prioritize the right work, secure buy‑in, and compound gains over time. Use the calculator to build your business case—and if you’d like hands‑on help, Bubble Marble can get you from audit to shipped improvements fast.