UK National Insurance Calculator

National Insurance is one of those deductions everyone sees on their payslip but few people fully understand. It is calculated separately from Income Tax, using its own thresholds and rates, and works differently depending on whether you are employed or self-employed.

This calculator works out exactly how much National Insurance you pay, whether you are on a salary or running your own business, using current UK rates.

How to use the National Insurance calculator

Choose whether you are employed or self-employed, then enter your annual salary or profit. The calculator shows your National Insurance bill for the year, broken down monthly, using the correct class and rates for your situation.

How National Insurance is calculated

Employees pay Class 1 National Insurance at 8% on earnings between £12,570 and £50,270 a year, and 2% on anything above that. Unlike Income Tax, there is no separate tax-free band above £12,570. You start paying National Insurance as soon as your earnings cross that threshold.

These thresholds are set for each tax year and reviewed at every Budget, so they can shift over time even if the headline rates stay the same. The £12,570 threshold is known as the primary threshold for employees, and the £50,270 figure is called the upper earnings limit. Both are shared with the Income Tax system, which is why the two calculations often line up at the same points even though they are worked out separately.

Self-employed people pay Class 4 National Insurance instead, on their profits rather than their salary, at a lower main rate of 6% between £12,570 and £50,270, and 2% above that. Class 2 National Insurance changed significantly from April 2024. It is no longer charged to most self-employed people above the small profits threshold, who are simply treated as having paid it for State Pension purposes. Below the threshold, it remains available as a voluntary payment for anyone who wants to protect their record.

Worked example

An employee earning £35,000 a year pays National Insurance on the £22,430 above the £12,570 threshold, all within the 8% band. That works out at around £1,794 a year, or roughly £150 a month.

A self-employed person with the same £40,000 profit pays Class 4 National Insurance instead. The first £12,570 is free of Class 4, the next £27,430 up to £50,270 is charged at 6%, giving a bill of around £1,646 for the year. Since their profit is above the small profits threshold, they owe no Class 2 National Insurance, though they are still credited towards their State Pension.

Why your National Insurance record matters

Beyond the money deducted from your pay each month, National Insurance builds up what is known as your qualifying years. You generally need around 35 qualifying years to receive the full new State Pension, and at least 10 to get any State Pension at all. Gaps in your record, from periods of low income, unemployment, or time spent caring for family, can sometimes be filled with National Insurance credits or voluntary contributions, which is worth checking on GOV.UK if you have had breaks in your working history.

Common mistakes to avoid

A common mistake is assuming National Insurance works like Income Tax, with a tax-free personal allowance. It does not. Every pound above the primary threshold is charged, with no separate nil-rate band. Another mistake, common among newly self-employed people, is not realising that Class 2 rules changed in April 2024. Many older guides online still describe the previous system, where Class 2 was a small flat weekly charge for almost everyone, which can lead to over budgeting for a bill that no longer applies in most cases.

It is also worth remembering that National Insurance is calculated separately from Income Tax, so a change in one does not automatically change the other. If you want your full tax and National Insurance picture together, our take-home pay calculator combines both in one result.

For anyone with more than one job, it is worth knowing that National Insurance is normally calculated separately for each employer, using the same thresholds for each job rather than combining your total income first. This is different from Income Tax, where HMRC does look at your combined income across jobs through your tax code. It means the amount of National Insurance you pay overall can sometimes be higher across two part time jobs than it would be on the same total income from a single job, so it is worth checking your specific situation carefully if this applies to you.

Related calculators

For the complete picture including Income Tax, pension contributions and student loan repayments, use our take-home pay calculator. If you are self-employed, our self-employed tax calculator combines Income Tax and Class 4 National Insurance in one place. You can also check our Income Tax calculator and income tax guide for more on how the two systems fit together.