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Lighthouse Score Calculator

Combine Lighthouse category scores into an overall weighted result.

About Lighthouse Score Calculator

The four categories are averaged equally, but performance is the only one measured from real timings, so it fluctuates between runs while the others are deterministic audits. Accessibility and SEO are largely fixable once, whereas performance requires ongoing attention, which is why the gap between them tends to widen over a project's life.

Formula

Lighthouse Score

Overall = mean of the four category scores

green threshold
Lighthouse marks 90 and above as good
performance
The only category driven by measured timings rather than audits

Worked example

With the default values below, Lighthouse Score Calculator returns Overall Score of 85.75. Change any input above and every figure here is recalculated in your browser.

Inputs used

Performance scoreaccepts 0–100 %
68 %
Accessibility scoreaccepts 0–100 %
88 %
Best practices scoreaccepts 0–100 %
92 %
SEO scoreaccepts 0–100 %
95 %

Results

Overall Score
85.75 /100
Rating
Needs improvement
Weakest Category
Performance
Points Needed to Reach 90
4.25
Performance Gap Against the Others
25.82%

Step by step

  1. 1Values used
  2. 2Lighthouse Score
  3. 3Overall Score= 85.75 /100
  4. 4Rating= Needs improvement
  5. 5Weakest Category= Performance
  6. 6Points Needed to Reach 90= 4.25
  7. 7Performance Gap Against the Others= 25.82

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 2 decimal places, 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 Lighthouse Score calculated?

Overall = mean of the four category scores The four categories are averaged equally, but performance is the only one measured from real timings, so it fluctuates between runs while the others are deterministic audits.

Why does Lighthouse Score matter?

Accessibility and SEO are largely fixable once, whereas performance requires ongoing attention, which is why the gap between them tends to widen over a project's life.

What values do I need to enter?

This calculator takes 4 inputs: Performance score, Accessibility score, Best practices score, SEO score. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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