There's a small calculation from a 1992 book that most people never do, even though it changes every buying decision for the rest of their lives. It's in the second chapter of Your Money or Your Life by Vicki Robin and Joe Dominguez, and it goes like this:

Your real hourly wage is not what your contract says.

The number on your offer letter — "$30 an hour" or "$85,000 a year" — is a gross rate. It's the top of a long subtraction problem. By the time you're actually handing money over at a store, you've paid for roughly half of what that paper number promised you. The other half got spent to make the paper number possible at all.

The subtraction

Walk through it with a real example. Say you earn $30 an hour, 40 hours a week, 50 weeks a year. That's $60,000 gross. Your hourly rate, on paper, is $30.

Now start subtracting.

Federal income tax, give or take — about 15% effective. Social Security and Medicare — 7.65%. State income tax — depends, but say 5%. That's 27.65% off the top, so you're down to roughly $43,400 take-home. Your rate is now $21.70 per actual hour you worked.

Now the invisible costs. Commuting: say 30 minutes each way, five days a week — that's 5 hours a week of unpaid time you wouldn't spend if you didn't have the job. Plus $100 a month for transit, or $400 a month if you drive (gas + insurance + depreciation attributable to commute). Call it $200/mo blended.

Work clothes, lunches out, coffee to stay awake: $250/mo easily, often more. Decompression spending — the dinner out on Friday because you're wrecked, the streaming subscriptions because you don't have energy to do anything else — another $150/mo.

Now redo the math with those subtractions. Deduct the cash costs from take-home ($43,400 - $7,200 = $36,200). Deduct the unpaid commute hours from the denominator (2,000 + 250 = 2,250 hours spent on work per year). New rate:

$36,200 ÷ 2,250 hours = $16.09 per hour.

That's the real number. A 46% discount from the paper $30. This is not unusual — Robin and Dominguez found the same 30-50% gap across hundreds of readers in the early 90s, and it's held up in every workbook replication since.

What changes when you use the real number

Take a $5.45 Starbucks Grande Latte.

Or a $1,199 iPhone 16 Pro.

A pattern emerges. Small purchases get a little more expensive in hours. Large purchases get dramatically more expensive. The $30k car that was "one year of work" becomes nearly two years. The $80k wedding is not six months — it's a year and change. This isn't about being miserly; it's about using the number that matches reality.

The 10-minute version

You don't need a spreadsheet. Here's the quickest honest pass:

  1. Take-home pay for last year. Look at your tax return line — the actual cash that landed in your account. Divide by 12 for monthly.
  2. Subtract job-related spending. Commute (money + unpaid time), work clothes, work lunches, work coffee, stress-decompression. Rough is fine.
  3. Count hours you actually give to the job. Paid working hours + unpaid overtime + commute + any work-for-tomorrow's-Monday that bleeds into Sunday.
  4. Divide. That's your real hourly rate.

Write the number somewhere you can see. Tape it to the inside of your wallet, if you still carry one. Before every purchase above $50, divide by that number. The answer is the hours of your life this thing costs — and once you've seen it a few times, you don't really need the wallet card any more.

Using it in HourSpend

The free calculator takes your real hourly wage and converts any purchase. The iOS app does it automatically for every expense you log, so the duration is always visible instead of buried. Both are built on the same framework Robin and Dominguez described thirty-three years ago — it still works because the math does not age.

Further reading: the philosophy page covers why this matters at a life level, not just a budget level.