How this guide works
Every chapter shares one plan. First you set a target pot, then each step (the years you give it, the tax wrapper it sits in, the blend of cash, bonds, stock indexes and bitcoin, and the fees and inflation drag) recomputes the same projection and writes a line on the running receipt, ending with what the pot pays you each year in retirement. Nothing is stored and no account is needed; the link you copy at the end carries your numbers in the URL.
How big does my retirement pot need to be?
A widely used shortcut is 25 times the yearly income your savings must provide, the inverse of the 4% withdrawal rule. In the UK, the Retirement Living Standards (Pensions UK, updated June 2026) price a minimum, moderate and comfortable retirement in pounds per year for singles and couples. In the US a common rule of thumb, quoted by the Social Security Administration, is to replace about 80% of pre-retirement income. Subtract what the State Pension or Social Security covers, and 25x the remainder is your target pot.
How much should I save for retirement?
A common rule of thumb is 10% to 15% of gross income, including any employer contribution, starting as early as you can. The honest answer from the first chapter is that the start date matters more than the amount: a modest monthly sum started at 25 routinely beats a much larger one started at 40, because the early money compounds for longer.
What return should I assume on my investments?
Over 1928 to 2025, US large-company stocks returned roughly 10% a year with dividends reinvested, 10-year government bonds roughly 4.6%, and cash-like Treasury bills roughly 3.3% (all before inflation; data from NYU Stern). The guide blends the stock and bond figures for your chosen mix. Lower assumptions are safer for planning, and a diversified portfolio can behave differently from the US market alone.
Do investment fees really matter?
More than almost anything else you can directly control. Fees are charged on the whole pot every year, so they compound against you: over a 35-year save, the difference between a 0.2% index fund and a 1.5% managed fund is routinely a five-figure sum, sometimes six. The fees chapter shows the exact cost at your numbers.
What is an employer match worth?
In the US, a typical 401(k) match adds 50 cents per dollar you contribute up to a slice of salary, an instant 50% return before any growth. In the UK, auto-enrolment requires a total of at least 8% of qualifying earnings into your workplace pension, of which your employer pays at least 3%, and basic-rate tax relief tops up your own contributions. The wrapper chapter shows what that boost compounds into by retirement day.
Is the 4% rule safe?
Mostly, historically. The drawdown chapter replays your blend through the worst retirement start years on record (1929, 1973, 2000 and 2008) with inflation-linked withdrawals, using the longest verified US return series. In most historical sequences a 4% starting withdrawal survived 40 years; in the worst ones it did not, and the fixes were flexibility on spending, retiring slightly later, or converting part of the pot to a guaranteed income. UK savers can also compare a level and an RPI-linked annuity at dated best-buy rates.
Figures are estimates for guidance only. Historical returns are nominal own-currency figures (Aswath Damodaran, NYU Stern, 1928 to 2025; MSCI 1998+; FTSE Russell 1986+; JST Macrohistory gilts) and do not predict future performance. Retirement Living Standards are Pensions UK figures dated June 2026; annuity rates are a dated best-buy snapshot; contribution limits and allowances cited are for the 2026 US tax year and 2025/26 UK tax year. Funds and ETFs shown are examples, not recommendations. This is not financial advice; consider speaking to a qualified adviser.