Why hours are an honest currency
The point isn't to never buy anything. The point is that hours are a more honest currency than pounds or dollars, because you can't earn more of them. Money comes and goes; the Tuesday afternoons you traded for it don't come back. Once a price tag turns into "a day and a half at my desk", you know instantly whether the thing is worth it.
It works both ways, which is the part people miss. Some purchases fail the test badly the moment you see the hours. Others pass with room to spare: the mattress you sleep on for eight years, the boots that outlast three cheap pairs, the flight to see someone you miss. Some things are absolutely worth the hours. This tool just makes sure you're deciding on purpose.
Worked example
Take the defaults: on $75,000 a year at 40 hours a week, the hourly rate is $36.06, so a $1,200 purchase costs 33.3 hours of work, about 4.2 working days. That's most of a working week. Maybe it's worth it. Maybe it very much isn't. Either way, "4.2 days" is a clearer question than "$1,200".
Frequently asked questions
Should I use gross or net salary?
Net gives the more honest number, because it's what actually reaches your account. Gross is the default here simply because it's the number most people know off the top of their head. If you know your take-home pay, use that instead.
Does this include commute time?
No, it only counts the hours you're paid for. Mentally add your commute and the getting-ready time on top and your real hourly rate drops, so everything gets expensive fast. I try not to think about it too often.
Is this just the latte factor?
Related but different. The latte factor is about what small repeated purchases cost over years, especially once you count the investment returns you gave up. This tool prices a single purchase in hours of work, right now. Use both and you get the full picture.