How to Calculate Your Retirement Savings Goal

Retirement planning requires estimating two things: how much you'll spend in retirement and how long your savings need to last. Getting these numbers right early gives you the most time to act.

Step 1 — Estimate Your Annual Retirement Spending

Most financial planners use 70–80% of pre-retirement income as a starting estimate, because:

• Mortgage is usually paid off
• Children are financially independent
• Work-related expenses disappear
• Taxes may be lower

Example: If you currently earn £60,000/year, estimate £42,000–£48,000/year in retirement.

Adjust up if you plan travel, healthcare costs, or major hobbies. Adjust down if you'll have a paid-off home and modest lifestyle.

Step 2 — Apply the 4% Rule (Safe Withdrawal Rate)

The 4% rule states that you can withdraw 4% of your portfolio in the first year of retirement and adjust for inflation annually — with a high probability your portfolio will last 30+ years.

Required savings = Annual spending ÷ 0.04
                 = Annual spending × 25

Example: £42,000/year → £42,000 × 25 = £1,050,000 required

This is a rough rule. If you retire at 55 and may live 40+ years, consider using 3.5% (× 28.6). If you retire at 70, 4.5% (× 22) may be appropriate.

Step 3 — Account for Other Income Sources

Reduce your required savings by guaranteed income sources:

Source	Example
State Pension (UK)	~£11,500/year (full new state pension 2026)
Social Security (US)	Varies; average ~$22,000/year
Defined-benefit pension	Check your annual statement
Rental income	Net rent after costs

Example: £42,000 needed − £11,500 state pension = £30,500 needed from savings Required portfolio = £30,500 × 25 = £762,500

Step 4 — Account for Inflation

£42,000 today will buy less in 20 years. Inflation erodes purchasing power at roughly 2–3% per year.

Future spending at 2.5% inflation:

Future value = Today's spending × (1 + 0.025)^years

Example: £42,000 today, retiring in 25 years:

42,000 × (1.025)^25 = 42,000 × 1.853 = £77,826/year needed

Your required portfolio also needs to be inflation-adjusted. Most retirement calculators handle this automatically by projecting real (inflation-adjusted) returns.

Step 5 — Calculate Monthly Savings Needed

If you're starting from zero and targeting a specific corpus:

Monthly saving = FV × r / [(1 + r)^n − 1]

Where FV = target amount, r = monthly return rate, n = months.

Example: Target £762,500 in 25 years, assuming 6% annual return:

• r = 0.06/12 = 0.005
• n = 300
• Monthly saving ≈ £1,110/month

Common Retirement Planning Mistakes

1. Starting too late. Compound growth needs time; 10 extra years of contributions makes a dramatic difference.
2. Underestimating healthcare costs. Medical expenses often increase in retirement.
3. Forgetting inflation. A fixed pension that looked generous at 65 may feel meagre at 80.
4. Withdrawing too early from tax-advantaged accounts. Penalties and tax costs can be significant.
5. Assuming stock returns will be constant. Sequence-of-returns risk (bad years at the start of retirement) can deplete a portfolio faster than averages suggest.

Use the Retirement Calculator to model your target age, savings rate, and expected returns in one place.