National Insurance calculator
Use this calculator to estimate UK National Insurance contributions for employed or self-employed income. It provides an annual estimate and shows equivalent monthly and weekly figures using current UK thresholds.
- Employee estimates use standard Class 1 primary rates and thresholds for the selected pay frequency.
- Self-employed estimates use Class 4 annual thresholds only and do not include voluntary Class 2 payments.
- This tool is scoped to standard UK cases and does not model special NI letters, multiple jobs deferment, or contracted-out history.
- Other employment income is treated as an additional annual amount for a simple combined estimate.
Your details
Enter your income, choose employed or self-employed, and select the frequency you want to use.
Results
Your National Insurance estimate appears here after calculation.
Ready when you are
Enter your income details and press calculate to see your estimated National Insurance.
National Insurance breakdown
| Item | Value |
|---|---|
| Employment type | — |
| Total income used | — |
| Primary / lower threshold | — |
| Main rate slice | — |
| Additional rate slice | — |
| Main NI amount | — |
| Additional NI amount | — |
| Total NI | — |
- Uses standard UK Class 1 or Class 4 NI rules.
- Shows annual, monthly, and weekly equivalents.
- Uses pay-frequency thresholds for employed estimates.
- Keeps to a simple planning estimate for standard cases.
How this National Insurance calculator works
A quick way to estimate UK NI on employment income or self-employed profits.
This calculator estimates National Insurance using the selected employment type and tax year. For employed income, it applies the relevant primary thresholds and rates based on whether you enter annual, monthly, or weekly pay. For self-employed income, it applies annual Class 4 thresholds to profits.
It is most useful as a budgeting tool when you want to understand how much NI may be due on a given level of income, or how NI changes if your pay frequency differs.
Because real payroll and Self Assessment calculations can include additional rules, this tool keeps the scope narrow and clear. It does not try to estimate every edge case, but it does provide a practical baseline for common UK scenarios.
Assumptions
Important scope notes for this estimate
Employed calculations
- Uses standard employee Class 1 primary NI rates and thresholds.
- Annual, monthly, and weekly estimates are based on the corresponding threshold set.
- Does not model special category letters, directors’ annual method, or deferment.
Self-employed calculations
- Uses Class 4 annual thresholds for self-employed profits.
- Voluntary Class 2 contributions are not added because they are not mandatory.
- Profits are treated as the NI base after allowable business deductions.
General scope
- Built for standard cases in the UK.
- Other employment income is treated as a simple annual add-on.
- Use payroll software or HMRC guidance for formal calculations.
Worked example
A simple illustration of how the estimate is built
Example: employed on £42,000 per year
If you are employed and your annual gross pay is £42,000, the calculator applies the annual primary threshold first and then calculates NI at the main employee rate on income above that threshold. Because the income is below the upper earnings limit, only the main rate applies.
The results panel then shows the estimated annual NI due, plus monthly and weekly equivalents for planning purposes.
Example: self-employed profit of £35,000
If you are self-employed and enter £35,000 as annual profit, the calculator applies Class 4 thresholds. NI is charged on the portion above the lower profits limit and below the upper profits limit, with no additional-rate slice unless profit exceeds the upper threshold.
How the Calculation Works
This tool estimates National Insurance by applying the selected year’s NI thresholds and rates to your earnings.
The calculator looks at your pay level and applies the main employee NI rate only to earnings above the threshold, then applies the additional rate to earnings above the upper limit where relevant. In self-employed mode it switches to the Class 4 style profit basis.
That makes it useful when you want to isolate NI rather than view a full payslip estimate.
Limitations
National Insurance is simple at headline level, but payroll details still matter.
This estimate assumes standard cases and does not attempt to cover every National Insurance category, directors’ calculation method, employer NI or unusual payroll adjustment.
It also isolates NI rather than replicating a full payslip, so differences can appear when real payroll software uses per-period or cumulative rules.
What to Do Next
Use the result as one part of a full earnings picture rather than a standalone decision tool.
Compare this estimate with the Income Tax Calculator and the Take Home Pay Calculator. Keep a placeholder for National Insurance Explained in the UK.
If you are modelling self-employed income, also use the Self-Employed Tax Estimator.
FAQs
Common questions about National Insurance
Does this calculator work for both employees and the self-employed?
Yes. You can switch between employed and self-employed modes. The calculation method changes to match the selected NI basis.
Why can monthly and annual NI differ for employees?
Employee NI is normally assessed per pay period in payroll. That means a monthly-paid employee can see a different pattern from someone paid weekly, even on the same annualised salary.
Does this include employer National Insurance?
No. This tool estimates the individual’s own National Insurance contribution only, not the employer’s secondary contribution.
Does self-employed NI include Class 2?
No. The estimator focuses on Class 4 because Class 2 is no longer generally payable as a mandatory contribution, though voluntary payments can still exist in some cases.
Can I use this if I have more than one job?
You can use the optional extra income field for a rough combined estimate, but real NI across multiple jobs can involve separate payroll calculations and deferment rules.
What does effective NI rate mean?
It shows NI as a percentage of the total income used in the estimate, giving you a simple sense of the NI burden on that level of earnings.
Is this calculator suitable for directors?
Not as a precise tool. Directors can have different NI treatment and annual methods, so this calculator keeps to standard employee cases.