Details are available on the UK government website via the link. The page provides details of contribution rates such as:
National Insurance rate for employees (how much employers withhold from employees’ wages/salaries from April 6, 2023 to April 5, 2024);
National Insurance rates for employers (how much employers pay towards employees’ National Insurance Contributions from April 6, 2023 to April 5, 2024).
It is also possible to calculate your contributions.