Work Out the Right Workplace Pension Contribution Rate

Paying the auto-enrolment minimum feels fine until you do the maths on what it actually buys you in retirement. Feed in your age, salary, current contributions and the income you'll want, and this works in real terms what rate gets you there, so you set the number on purpose rather than leaving it on default.

I want to decide how much to contribute to my workplace pension beyond the minimum. Here are my details:

- Age: {AGE}
- Gross annual salary: {GROSS_SALARY}
- Current employee contribution: {CURRENT_EMPLOYEE_PERCENT}%
- Employer contribution: {EMPLOYER_PERCENT}%
- Target retirement age: {TARGET_RETIREMENT_AGE}
- Estimated retirement income needed (today's money): {TARGET_ANNUAL_INCOME}

Using a real-terms growth rate of 3% and inflation of 2.5%, calculate: (1) my projected pot at retirement on current contributions, (2) how large a pot I need to fund my target income to age 90, (3) the contribution rate required to close any gap, and (4) the immediate net-pay cost of increasing contributions given my income-tax band. Present a clear recommendation with sensitivity ranges.