National Insurance Contributions Calculator
This National Insurance calculator covers both employee Class 1 NI (deducted via PAYE) and self-employed Class 2 and Class 4 NI. It uses 2024-25 thresholds following the 2pp cut to 8% (employee) and 6% (self-employed Class 4) effective January 2024.
Educational estimate. Calculator results are for planning and information only, not financial, tax, medical, legal, or engineering advice. Verify important decisions with official sources or a qualified professional.
National Insurance Contributions Calculator
Class 1, 2 & 4 NI — Employee & Self-Employed
📐 Formula & Method
Class 1 (Employees) 2024-25
Rate reduced from 10% to 8% from 6 January 2024. Employer also pays 13.8% above Secondary Threshold.
Class 4 (Self-Employed) 2024-25
Class 4 rate cut from 9% to 6% from 6 April 2024. Class 2 contributions from April 2024 are voluntary but still count toward State Pension.
📋 How to Use
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1
Enter your annual earnings or self-employed profit.
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2
Select employed or self-employed.
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3
See your annual NI contribution broken down by band.
National Insurance — 2024-25 Rates Explained
National Insurance funds the NHS, State Pension, and other benefits. Employees pay Class 1 NI; employers pay a separate employer NI contribution (not shown here). Self-employed people pay Class 4 NI on profits and can voluntarily pay Class 2 to protect their State Pension entitlement.
The 2024 Spring Budget reduced the employee Class 1 main rate from 10% to 8% and the self-employed Class 4 main rate from 9% to 6%, saving the average employee around £450 per year.
🔬 Methodology & Accuracy
Formula: Uses the standard mathematical formula shown in the Formula & Method section above. All computations run client-side in your browser — no data is sent to our servers.
Data sources: Tax bands, contribution limits and regulatory rates are taken from official US (IRS, SSA) and UK (HMRC, gov.uk) publications for the current tax year, and updated when bands change.
Last reviewed: January 2025 · Accuracy: Results are precise to two decimal places using IEEE-754 double-precision arithmetic. Intended for educational and planning use only.
For informational purposes only. Results are estimates based on the inputs and formulas provided. For financial, tax, medical, or legal decisions, consult a qualified professional. Rates and regulations change — always verify current figures with official sources.