How Inflation Doubles Your Retirement Number

Inflation is the steady rise in prices over time. In most developed economies it averages 3–6% a year, and in many developing ones it runs higher. The problem isn't the yearly figure itself. It's the way it compounds.

At 5% inflation, prices double in about 14 years, triple in 23 and quadruple in 28. So if you're 30 now and plan to retire at 60, the cost of the life you live today will have more than quadrupled by the time you stop working. Then it keeps climbing for the 20–30 years you spend in retirement.

Very few retirement plans face up to this. People do the sums once, decide that "$4,000/month gives me $1.2 million over 25 years", and call it a plan. But they've budgeted in today's dollars, not the ones that will actually arrive in their account three decades from now.

Let's say you spend $3,000 a month today on housing, food, healthcare and everything else. That's $36,000 a year. Now imagine you retire in 30 years, with inflation at 5%.

Put that into the Retirement Expense Inflation Planner and your first year of retirement no longer costs $36,000. It costs about $155,500. The monthly amount that buys exactly the life you have now isn't $3,000 any more, but $12,960.

And that's only the first year. The second costs 5% more. By the tenth year it's about $20,100 a month, and by the twenty-fifth, the same lifestyle costs just over $41,800 a month.

Add up every year of retirement and you get your total spending in future dollars, the amount you'll literally hand over. For our $3,000-today example, over 25 years of retirement at 5% inflation, that comes to roughly $7.4 million.

You don't need $7.4 million on the first day, though, because your savings keep earning while you're retired. Most plans assume a moderate return after retirement, say 7%, from lower-risk investments.

Run the same example through the present value of a growing annuity (the standard formula for this) and the pot you need on retirement day falls to roughly $2.9 million. That's still a long way from the "$1.5 million should be enough" you might have read on a finance blog back in 2010.

The popular shortcut, saving 25 times your yearly spending and then withdrawing 4% a year, does allow for inflation. It quietly assumes a 7% return before inflation, 3% inflation, and a 4% withdrawal you can keep up in real terms.

That works well enough if you're retiring in five years, because you can take today's spending and multiply. It works less well if you're thirty years away, because the yearly spending you should be multiplying by 25 is the spending of 2055, not of today.

Put today's $36,000 into the rule and you get a $900,000 target, a number that's already out of date the moment you write it down. Apply the same rule honestly, to the future spending of $155,500, and you get roughly $3.9 million, much closer to what the planner shows.

One assumption does more work than any other: the return your money earns once you've retired. The size of the pot you need is extremely sensitive to it.

Raising your assumed return by 1 point (say from 6% to 7%) doesn't just trim a few percent off the target. Because the calculation depends on the gap between your return and inflation, even small changes move the answer by 20–40%.

That's why staying invested through retirement matters so much. Someone who moves everything into a low-interest bank account at 65 might earn 3% while inflation runs at 5%, so their money shrinks in real terms. The same person with a balanced portfolio earning 7% could make 2% a year above inflation, and need millions less at the start to fund the same life.

1. Start with the Retirement Expense Inflation Planner. Enter what you honestly spend now (not what you'd like to spend) and a cautious inflation rate, and note the target it gives you.
2. Run the Retirement Calculator with your current savings, monthly contributions and expected return before retirement. Compare what you're on track to build with what you need.
3. If there's a gap, use the Recurring Investment Calculator to work out the monthly amount that would close it. It's a conversation worth having with your future self today.
4. Re-run the plan every two to three years, or whenever your income, spending or timeline changes. Inflation assumptions that made sense in 2020 may not hold in 2030, so keep them up to date.

The first mistake is using today's spending without inflating it. The numbers feel comfortable and the plan feels doable, but by the time the gap appears, decades of compounding can't be won back.

The second is being too hopeful about returns before retirement and too gloomy about returns after it. Optimism early on makes the target look easy, and pessimism later makes the pot look enormous. The reality is often the other way round: balanced portfolios have returned 8–10% before retirement in many countries, and sensible income portfolios after retirement often manage 6–7%.

The third is forgetting that healthcare costs rise faster than prices in general in most economies. If general inflation is 5%, plan for 7% on a retirement budget with heavy medical costs. It makes a real difference to the pot.

The fourth is planning for too short a retirement. People are living longer, and planning to age 80 when many now reach 90 leaves a decade of costs uncovered. Use a cautious life expectancy, 90 or more if you're in good health and your family tends to live long.

If you're more than ten years from retirement, the number in your head is very probably too low. Inflation works slowly and quietly, and every year it's ignored, the gap grows.

So run the planner, find your real number, and build a savings plan that gets you there. The maths isn't comfortable, but finding out at 65 that your savings cover only 12 years of what was meant to be 25 is far harder.