// multi-utility computation suite · offline · instant · precise
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│ [c] calcalyst_ │
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build.web-fid Calculator
Calculates First Input Delay (FID) from main thread blocking duration and estimates the proportion of users experiencing 'good' (<100ms) vs. 'poor' (>300ms) interactivity. FID was deprecated in favour of INP in 2024 but remains in legacy performance reports and older Lighthouse audits.
Inputs
Long Task Ms
Reference formula or conversion factor shown for context.
Script Kb
Reference formula or conversion factor shown for context.
Parse Ratio
Duration of the process. Make sure units match the rate inputs (seconds, minutes, or hours).
Results
FID estimate
The value at the specified point or condition.
TBT estimate
The value at the specified point or condition.
rating
A standardised quality or risk rating on the applicable scale.