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The Math

Coffee versus investing: the 30-year math, and the number everyone leaves out

Every finance channel shows you that your coffee costs you a small fortune. That part is right. What is missing is roughly half of it.

by · Published · Last reviewed · 6 min read

The same amount over three periods: Per week $17, Per month $73, Per year $875.Per week$17Per month$73Per year$875

You buy a coffee every working day for $3.50. That is $17 a week and $875 a year. Dull so far, and still it surprises most people: nobody ever writes that number on a bill, and it arrives every year all the same – in units of $3.50.

Now the part you already know

Invest that same $73 a month for 30 years at a 5 percent annual return and you end up with $59,457. That is the number in every other video, usually with an exclamation mark and a shocked face on the thumbnail.

The number is calculated correctly. It is still misleading, for two reasons that rarely get a mention.

Reason one: most of it is your own money

Of that $59,457, you paid in $26,251 yourself. Compounding added $33,206. That is a lot, but it is not coffee turning into a fortune – it is mostly thirty years of not spending.

Reason two: 2056 dollars are not 2026 dollars

At 2 percent annual inflation, $59,457 thirty years out buys what $32,825 buys today. Still an excellent result for a skipped coffee. Just not the headline number – a little over half of it.

Why we use 5 percent and not 7

Elsewhere you will see a higher figure, usually 7 percent. What almost nobody says is whether that figure is before or after inflation – and it is quoted both ways. Take it as a nominal number and subtract inflation on top, and you have subtracted it twice; take it as a real number and stop there, and you have not subtracted it at all. We sidestep the question: 5 percent is our nominal assumption after fund costs, and inflation comes off visibly afterwards. Both are assumptions, and both are printed under every result.

Run it with your own coffee

This calculation runs on our server and is not stored – neither your result nor your entry.

per week

$17

per month

$73

per year

$875

Once $3.50
Times per year (every working day) 250.00
Per year $875
Invested as a monthly amount $73
After the period, nominal $59,457
Of that, in today’s purchasing power $32,825

Assumptions behind this calculation

  • Assumed return per year: 5.0%
  • Assumed inflation per year: 2.0%
  • Period considered: 30
  • Calculated as if the annual amount were invested in twelve monthly installments.

The full calculator with an example, the method and sources: Habit Cost Calculator: What a Daily Coffee Costs a Year

And now the uncomfortable question

Nobody actually invests their coffee. The calculation shows an order of magnitude, not a statement of account – and it works with any habit, not only the one that lectures well. An evening beer, a pack of cigarettes, a parking garage instead of a ten-minute walk: same math, same order of magnitude.

The point is not that you should give up the coffee. The point is that recurring is the most expensive property an expense can have, and that we systematically miss it on small amounts and never miss it on large ones. Everyone thinks twice about an $875 purchase. Nobody thinks twice about $3.50 – not even when it is the same $3.50, 250 times over.

What you can do about it

  1. Keep the coffee, cut a different habit

    Put your three largest recurring expenses into the calculator above – not the ones that make for easy jokes. Very often the top of that list is something you do not care about, while the coffee that holds up half your morning is the cheapest item on it.

  2. Turn the number into a standing order, not a resolution

    If you do want to invest: set the transfer for the day after payday, not for the end of the month. What is left at the end of the month is, by definition, what happened to be left – and in the month the washing machine dies, that is nothing.

  3. Start with the emergency fund, not the brokerage account

    Without a cash buffer, the first emergency forces you to sell at exactly the wrong moment. How much you need and where it belongs is in Emergency fund: how much you actually need.

Frequently asked

Is a 5 percent return realistic?

It is an assumption, not a promise. Thirty years contains decades where it was considerably less, and decades where it was more. Anyone naming a number for the future is naming an assumption – so we print ours under every result instead of hiding it in the small print.

Why 250 working days?

52 weeks times 5 days is 260, minus the 10 or so days most workplaces close for. There are 12 permanent federal holidays, but they bind federal employees, not private employers[1] – and there is no statutory leave at all. If your year looks different, change the rhythm in the calculator: it is a field, not a fixed value.

Is tax included?

No. Capital gains and dividends are taxed, and how much depends on your account type and jurisdiction. The figure above is therefore the upper edge. We would rather say so than print a bigger number.

This article has been corrected. What was wrong is on the corrections page, with the date. See all corrections

This article is not investment advice. We describe how things work and what they cost. What fits your situation is yours to judge – if in doubt, with someone who knows it.

Sources

  1. Federal Holidays: Evolution and Current Practices (CRS Report R41990): twelve permanent federal holidays, one of which (Inauguration Day) falls every four years and only in the District of Columbia area; federal holidays apply to federal employees and do not oblige private employers, Congressional Research Service, Library of Congress, retrieved August 26, 2026.

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