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Page Speed Budget Calculator

Set a connection speed, an LCP target, and your current page weights — get a per-resource budget with overage warnings. Instantly see which bucket to trim first.

5 connection presetsLCP-derived KB budgetPer-resource breakdownWorst-category flagLoad-time estimateCSV exportIn-browser only

Budget inputs

1

Target connection speed

Plan for your slowest common user. Mobile 4G is the typical worst-case for Australian consumer sites.

2

LCP target

Google's "Good" threshold is 2.5s. Subtract rendering overhead (~0.5s) to get the network budget.

3

Current page weights (KB, transferred)

Open Chrome DevTools → Network → reload → Total transferred per type. Enter each bucket below.

Budget vs reality

Status4171% over budget
Total budget
48 KB
at Fast 3G (190 kbps)
Current weight
2050 KB
Load: ~86.3s network
Network budget
2.0s
2.5s LCP – 0.5s render

Per-resource budget

Resource
Share
Budget
Current
Overage
Fix
HTML
8%
4 KB
35 KB
+775%
Minify, enable gzip/br, ship shell only
CSS
18%
9 KB
180 KB
+1900%
Inline critical CSS, async rest, drop unused rules
JavaScript
30%
14 KB
620 KB
+4329%
Code-split by route, defer non-critical, tree-shake libs
Images
35%
17 KB
1100 KB
+6371%
Resize, AVIF/WebP, lazy-load below fold
Fonts
6%
3 KB
90 KB
+2900%
Self-host, subset Latin, woff2 only, font-display: swap
Other
3%
1 KB
25 KB
+2400%
SVGs, JSON, video — keep under 50KB each
Recommendations
  • errorPage is 2050KB — more than 2× the 48KB budget. Expect LCP 2× your target on Fast 3G.
  • warningBiggest gap: Images is 6371% over budget. Resize, AVIF/WebP, lazy-load below fold.
  • warningJavaScript at 620KB (transferred). Over 500KB is a heavy JS app — check for unused framework bundles and third-party scripts.

How to Set a Realistic Page Speed Budget

Four rules for translating Core Web Vitals targets into concrete engineering constraints.

1

Start from LCP, work backwards

Pick your LCP target (2.5s for Google "Good"). Subtract ~0.5s for CPU decode and rendering. What's left is your network budget — multiply by bandwidth to get your KB ceiling.

2

Plan for your slowest reasonable user

Desktop cable is easy. Mobile 4G is your realistic baseline for most Australian consumer sites. Fast 3G is the edge case worth checking if you serve rural or international traffic.

3

Attack images first

Images are 50–70% of page weight on most sites. Modern formats (AVIF, WebP), responsive srcset, and aggressive lazy loading cut 60–80% with zero perceived quality loss.

4

Enforce the budget in CI

A budget on paper is aspirational. A budget in your pipeline (Lighthouse CI, bundlesize, webpack-bundle-analyzer) is a guarantee. Fail builds that exceed it.

Budget Reference by Site Type

Starting points. Your actual budget depends on traffic, device mix, and tolerance for risk.

Landing page

Budget: 400–600KB total. Images dominate. Every KB costs you conversions on mobile — trim ruthlessly.

Blog / content

Budget: 700–900KB total. Feature image + body text + a bit of JS. No need for heavy frameworks.

E-commerce product

Budget: 800KB–1.2MB. Multiple product images + reviews + scripts. Lazy-load everything below the first image.

SaaS homepage

Budget: 700–900KB. Marketing pages should not ship the main app bundle. Code-split ruthlessly.

SaaS app shell

Budget: 1–2MB for first interactive. Code-split routes, ship only what the current screen needs.

News / publisher

Budget: 1–1.5MB. Ad loads inflate this. Aim for <500KB before-ad baseline; let ads push the total.

Internal B2B

Budget: 1.5–3MB. Users are on cable, tolerance for weight is higher. But still — lazy load everything.

PWA / installable

First load: 1–2MB. Repeat loads: <100KB (Service Worker cache hits). Design for both states.

Where Page Weight Usually Comes From

The recurring culprits we find in every performance audit.

JavaScript bloat

Full-framework SPAMoment.js / lodash fullDuplicate React bundlesThird-party tag overloadUnused polyfillsNo code splitting

Image waste

Original-size PNGsNo AVIF/WebPNo responsive srcsetHero lazy-loaded wrongGIF animationsBackground-image PNGs

Font over-serve

Multiple weights + italicsFull-unicode setsGoogle Fonts externalNo font-display: swapTTF/OTF not woff2Decorative fonts unused

Render blockers

Sync external scriptsNo async/deferInline CSS 500KB+Chat widget blockingAd SDKs head-inserted@import CSS chains

Page Speed Budget FAQ

What's a good page weight budget?

For mobile 4G with 2.5s LCP target: aim for under ~500KB transferred before LCP paints. For a full page: under 1MB is excellent, 1–2MB is acceptable, over 2MB is slow on anything but fixed broadband.

Which connection speed should I plan for?

Plan for your slowest common user. For consumer sites in Australia: fast 3G–4G is a good worst-case. For rural or emerging markets: slow 3G. For internal B2B tools: cable is fine.

What's the biggest win on most pages?

Images — usually 50–70% of total page weight. Modern formats (WebP/AVIF), responsive srcset, and aggressive lazy loading below the fold can cut image weight by 60–80% with no quality loss.

Is my input sent anywhere?

No. All calculations run locally in your browser. Nothing is uploaded or stored.

Want Lighthouse CI & Budget Enforcement Set Up?

Our Australian team sets up performance budgets in your CI pipeline — build failures when pages exceed budget, trend graphs in Slack, automated regression catches.

  • CI budget enforcement
  • Weekly perf regression alerts
  • No lock-in commitment
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