Best UK Pension Calculators 2026: Which? Alternatives, FIRE and Salary Sacrifice

The Pensions and Lifetime Savings Association suggests a "comfortable" retirement requires about £43,100 per year for a single person. Assuming a 4% withdrawal rate, that means a pension pot of roughly £1,075,000 on top of the full state pension. The actual amount depends on your lifestyle, location, whether you own your home outright, and when you plan to retire.

A common rule of thumb is to have saved roughly 3x your annual salary in your pension by age 40. So if you earn £40,000, you would aim for about £120,000 in your pension pot by that age. This assumes you started contributing in your mid-twenties and plan to retire around 67. If you started later, you will need to contribute more aggressively to catch up.

The 4% rule states that you can withdraw 4% of your portfolio in the first year of retirement, then adjust for inflation each year, and your money should last at least 30 years. It was derived from US stock and bond data, but the principle applies in the UK too. Some UK-focused analyses suggest 3.5% is safer given lower historical UK equity returns. It is a useful starting point, not a guarantee.

FIRE stands for Financial Independence, Retire Early. You reach financial independence when your investment portfolio can cover your annual expenses indefinitely, typically using the 4% rule. To calculate it, multiply your annual expenses by 25 to get your target number, then work out how many years of saving and investing it will take to reach that amount based on your savings rate and expected returns.

Salary sacrifice is almost always worth it because both you and your employer save on National Insurance contributions, meaning more money goes into your pension for the same cost. A higher-rate taxpayer sacrificing £1,000 of salary could see £1,138 or more land in their pension after employer NI savings are passed on. The main trade-off is that it reduces your gross salary, which can affect mortgage affordability assessments and some salary-linked benefits.

You can currently access your private pension from age 55 (rising to 57 from April 2028). The state pension age is 66, rising to 67 between 2026 and 2028, and to 68 in later years. When you access your private pension, you can take up to 25% as a tax-free lump sum and draw the rest as taxable income through drawdown or an annuity.

Which? is useful if you want broader retirement education, drawdown content, and pension tax explainers. Boring Math is a better alternative when you want a fast pension projection tool with no signup and direct routes into salary sacrifice, FIRE, and tax-planning follow-up calculators.

The Salary Calculator is helpful when you want to see how pension deductions affect take-home pay. Boring Math is a better alternative when your main goal is long-term pension planning, retirement-pot forecasting, or deciding how much extra to contribute before modelling the payslip impact separately.

Use a pension calculator when you want to know whether your retirement pot will be large enough. Use a salary sacrifice calculator when you want to know the short-term cost of increasing contributions through payroll. The best planning flow is usually pension calculator first, salary sacrifice calculator second.