Most solo founders don't have a spending problem. They have a decision-avoidance problem. A tool gets added during a busy month, it does its job well enough, and it quietly renews every month after because canceling requires you to stop and think about whether it's actually worth it. Eighteen months later you're paying for six tools that each do 80% of what one would, and nobody ever sat down to do the math.
The fix isn't a budgeting app or a New Year's resolution to "audit your tools." It's a formula you can run against any subscription in under two minutes, and a 20-minute session once a quarter to run it against everything you pay for.
Here's the whole thing:
Tool is worth it if: Monthly cost < (Hours saved per month x Your hourly rate)
That's it. If a tool costs less than the value of the time it hands back to you, keep it. If it costs more, it's either not saving you what you think, or it's a candidate to cut, downgrade, or replace.
The two inputs you need:
Say your hourly rate is $60. Here's an audit of four subscriptions:
Tool A -- project management software, $29/month. You use it to track client deliverables instead of a shared doc. It saves you maybe 30 minutes a week of "wait, what was I supposed to send them" scrambling -- call it 2 hours/month.
Math: 2 hours x $60 = $120 in value. Cost is $29. Keep it -- it's returning 4x what it costs.
Tool B -- a niche design tool, $49/month. You used it heavily for one client project four months ago. Since then you've opened it twice.
Math: roughly 0.25 hours/month saved x $60 = $15 in value. Cost is $49. Cut it. You're paying $34/month more than it's worth, and you can always resubscribe the next time a project actually needs it.
Tool C -- invoicing software, $15/month. It auto-generates and sends invoices, and chases late payments so you don't have to write those emails yourself. Conservatively, that's 1.5 hours/month of avoided admin.
Math: 1.5 x $60 = $90 in value. Cost is $15. Keep it, obviously -- and this is usually the easiest category to justify, because the manual alternative (writing invoices and follow-ups by hand) is tedious in a way that's easy to underestimate.
Tool D -- email marketing platform, $79/month. You send a newsletter twice a month to a list of 400 people. It takes you about the same amount of time to write and format the email whether the platform costs $79 or $20, because the tool isn't the bottleneck -- your writing is. The only time saved is automated scheduling and list management, maybe 1 hour/month.
Math: 1 x $60 = $60 in value. Cost is $79. This is the interesting case -- not a clear cut, but a signal to check whether a cheaper plan on the same platform (fewer contacts, fewer send credits) would cover your actual usage. You're not being told to cancel; you're being told to check if you're overpaying for headroom you don't use.
Total before the audit: $172/month. After acting on it: $104/month, plus a note to revisit Tool D's plan tier. That's roughly $800/year found in twenty minutes, without cutting anything that was actually earning its keep.
The formula breaks down for tools where the value isn't hours saved but risk avoided -- accounting software that keeps you audit-ready, or backup and hosting reliability that protects you from a catastrophic loss. For those, don't force an hours-saved number. Ask instead: "what does it cost me if this fails and I don't have this in place?" A $30/month accounting software subscription that keeps your books clean isn't competing against the hours it saves this month -- it's competing against the cost of a scramble at tax time, or the hours a bookkeeper would charge to reconstruct a year of transactions.
Run this quarterly, not once. Tools that earn their spot today can quietly stop being used six months from now, and the whole point is that you shouldn't have to trust your memory to notice.