Web Performance Budget Calculator
NewWork out how many KB of JavaScript, CSS, images and fonts fit in your page budget for a target load time on 3G, 4G or cable connections.
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| Resource | Share | Budget |
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Budget = (target time − round trips × RTT) × bandwidth, derated 20% for TCP slow start and protocol overhead. Sizes are transferred (compressed) bytes. Shares are a typical starting split; adjust to your site.
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Frequently Asked Questions
What is a performance budget?
A set limit on page weight or timing that keeps a site fast, enforced during development.
How are budgets calculated?
From connection speed, latency and your target time, leaving room for the HTML and round trips.
Are results exact?
They are estimates. Verify with Lighthouse or WebPageTest on real devices.
Which connection should I target?
Many teams target a mid-range phone on slow 4G.