Interaction to Next Paint Calculator

Break INP into input delay, processing and presentation delay.

About Interaction to Next Paint Calculator

INP replaced First Input Delay because it measures every interaction rather than only the first. A large input delay means the main thread was already busy when the user acted. Long tasks are the usual cause of poor INP, and breaking work into chunks under 50 ms is the standard remedy.

Formula

Interaction to Next Paint

INP = input delay + processing time + presentation delay

good threshold: 200 ms
input delay: Waiting for the main thread to become free

Worked example

With the default values below, Interaction to Next Paint Calculator returns Interaction to Next Paint of 240. Change any input above and every figure here is recalculated in your browser.

Inputs used

Input delayminimum 0 ms: 80 ms
Event processing timeminimum 0 ms: 120 ms
Presentation delayminimum 0 ms: 40 ms
Long tasks blocking the main threadminimum 0: 3

Results

Interaction to Next Paint: 240 ms
Rating: Needs improvement
Largest Contributing Phase: Event processing — break up long handlers
Milliseconds to Save to Reach Good: 40 ms
Estimated Blocking From Long Tasks: 150 ms

Step by step

1Values used
2Interaction to Next Paint
3Interaction to Next Paint= 240 ms
4Rating= Needs improvement
5Largest Contributing Phase= Event processing — break up long handlers
6Milliseconds to Save to Reach Good= 40 ms
7Estimated Blocking From Long Tasks= 150 ms

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Interaction to Next Paint calculated?

INP = input delay + processing time + presentation delay INP replaced First Input Delay because it measures every interaction rather than only the first. A large input delay means the main thread was already busy when the user acted.

Why does Interaction to Next Paint matter?

Long tasks are the usual cause of poor INP, and breaking work into chunks under 50 ms is the standard remedy.

What values do I need to enter?

This calculator takes 4 inputs: Input delay, Event processing time, Presentation delay, Long tasks blocking the main thread. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.