The Lighthouse Accessibility score is a weighted average of all accessibility audits. Weighting is based on axe user impact assessments.
Each accessibility audit is pass or fail. Unlike the Performance audits, a page doesn't get points for partially passing an accessibility audit. For example, if some buttons on a page have accessible names, but others don't, the page gets a 0 for the Buttons do not have an accessible name audit.
The following table shows the weighting for each accessibility audit. More heavily weighted audits have a bigger effect on your score. Manual audits aren't included in the table because they don't affect your score.