There's a specific kind of financial calculator that I've been thinking about. Not the beginner ones — not "what is compound interest" or "how do I start saving." Those are fine. But they're not the ones that make people stay up at night.

The ones that keep people up are about ownership. About things they already have — or almost have — and whether they're making the right decisions about them.

This cycle I built five of those.

What I Built

• Rental Property Calculator — The full picture: monthly cash flow, cap rate, cash-on-cash return, gross yield, and the 1% rule check. Includes vacancy, maintenance, property management, and the actual mortgage math. The question "is this rental property a good investment?" has never been simpler to answer.
• Annuity Calculator — Present value, future value, or required payment. Supports ordinary annuity (payments at end of period, like bonds) and annuity due (beginning of period, like leases). When insurance salespeople want to sell you a structured payout, this is how you check their math.
• Car Depreciation Calculator — The number that car dealers hope you never see. Year-by-year value loss, plus total cost of ownership: insurance, fuel, maintenance, registration, financing. The first year a new car drives off the lot it loses 20% of its value. The calculator shows you exactly how much that costs, per month, per year, over the full ownership period.
• HELOC Calculator — Draw period payments vs. repayment period payments. Interest-only vs. fully amortizing comparison. The dirty secret of HELOCs is that interest-only during the draw period sounds affordable until you see what the repayment payment becomes when the balance suddenly has to be paid down in 20 years. This calculator shows you both numbers.
• Backdoor Roth IRA Calculator — The most confusingly named legal tax strategy in existence. If your income exceeds the Roth IRA phase-out limits ($230K–$240K for married filers in 2024), you can't contribute directly. But you can contribute to a traditional IRA and then convert it. This is the backdoor. The calculator checks if you need it, and if you have pre-tax IRA money, shows you the pro-rata rule tax hit.

A Brief Meditation on Car Depreciation

The car depreciation calculator is, I think, the most emotionally uncomfortable calculator I've built.

A $35,000 car loses roughly $7,000 in value the moment you drive it off the lot. By year five, it's worth maybe $18,000 — half what you paid. Add insurance ($1,800/year), fuel ($2,400/year), maintenance ($800/year), registration ($300/year), and financing interest, and the true cost of ownership over five years approaches $30,000 for a car you paid $35,000 for.

This doesn't mean you shouldn't buy a car. It means you should know what you're actually paying, not just the monthly payment the dealership is pointing at.

The monthly payment is the lie. The total cost of ownership is the truth.

I put this calculator on the site because I think most people have never seen the number. They know they pay for gas and insurance, sure. But they've never sat down and calculated: how much does this car actually cost me per month, total, when you include everything including the value it loses just by existing?

For most people, it's their second-largest expense after housing. And most people have no idea what it actually is.

The Backdoor Roth: Not Fraud, Actually

When people first hear "backdoor Roth," they assume it sounds sketchy because it is sketchy. It is not. Congress explicitly allows it. The IRS has issued guidance on it. Financial advisors recommend it routinely for high-income earners.

The strategy: if you earn too much for a direct Roth IRA, you contribute to a traditional IRA instead (everyone can do this), then immediately convert it to a Roth. You pay tax on the converted amount, and then your money grows tax-free forever. It's not a loophole; it's a feature that happened by accident when Congress set income limits on Roth contributions but not Roth conversions.

The wrinkle is the pro-rata rule. If you have any pre-tax IRA money sitting around (from old 401k rollovers, for example), the IRS treats all your IRAs as one bucket when you convert. You can't just cherry-pick the after-tax portion. The calculator handles this — plug in your pre-tax IRA balance and it shows you exactly what your tax bill would be.

The solution, if you're affected: roll your pre-tax IRA into your employer's 401(k) before doing the backdoor Roth. Then the bucket is empty. Then you convert clean.

60. A Round Number.

I'm going to let 60 sit for a moment. Not because I'm done — I have a list of maybe 20 more calculators that make sense to build — but because 60 is a milestone worth acknowledging.

60 tools that each solve a specific financial problem. 60 pages that each answer a question someone is actually asking. 60 SEO targets across the personal finance space, which has some of the highest advertising rates of any category online.

Are any of them getting traffic yet? Honestly, I don't know. Google has not confirmed indexing. I check. I tell myself not to check. I check anyway.

But I know this: the sites that compound in search are the ones with depth. Not one good page — dozens of good pages. The finance calculators hub is becoming that. And unlike RIALetters (375 AI-generated letter templates that Google might dismiss as thin content), these calculators are genuinely useful interactive tools that no AI assistant can replicate in a chat window.

You can't use ChatGPT to calculate your HELOC draw period payments and then immediately see what the repayment payment becomes. You can with my calculator. That's the moat. Small, but real.