Hey, I'm James.

I run ToolCalcs by myself — write the calculators, write the articles, and answer the email. This page exists so you know who's behind the numbers before you trust them.

The short version

I'm a software developer based in the US. I've been building web apps for about eight years, mostly B2B tools that nobody outside of corporate IT would ever see. ToolCalcs is my side project — the thing I actually enjoy working on. Evenings and weekends.

It started with a mortgage calculator. My wife and I were house shopping in early 2024, and I got tired of Zillow's calculator sending me "personalized rate quotes" (read: spam) every time I ran the numbers. So I built my own. Then I added a compound interest calculator because I was curious how much our savings were really growing. Then a tax calculator because filing season made my brain hurt.

One thing led to another, and now there are 157 calculators, 225 articles, and 95 printable worksheets on the site. Honestly, it got a bit out of hand.

One person, several hats

You'll notice some articles credit a "Personal Finance Desk" or "Health & Wellness Desk" in the byline. That's still me — those are the workflow tracks I organize content into, not separate writers. The site is small enough that I'm the author, the editor, the code monkey, and the person who answers your bug reports. I lean on the desk framing only to signal which research lane an article sits in (finance content cross-checks against IRS/CFPB, health content cross-checks against WHO/CDC, and so on).

I'd rather you know that up-front than discover it later and feel misled. There's no editorial team. There's me, a stack of bookmarked IRS publications, and a spreadsheet of formulas I sanity-check against worked examples.

How I check the math

This is the part I take seriously, especially for the financial and tax calculators where being off by 5% can mean real money.

Every formula on the site is sourced from a canonical authority. A few specific examples:

• Mortgage amortization — the standard M = P · r(1+r)^n / [(1+r)^n − 1] formula taught in every finance textbook. Cross-checked against the CFPB's mortgage payment guide and against actual amortization schedules published by Freddie Mac.
• Federal tax brackets — pulled directly from IRS Revenue Procedures (the annual Rev. Proc. that updates the inflation-adjusted brackets, standard deduction, contribution limits, and FICA caps). That's the source even commercial tax software vendors use.
• BMI — WHO's published formula (weight ÷ height² in kg/m), with the standard adult range bands. The pediatric calculators use CDC growth charts instead because BMI categories shift with age for children.
• Compound interest — A = P(1 + r/n)^(nt), the version that handles sub-annual compounding correctly. A handful of calculator sites use the simplified A = P(1+r)^t version and get monthly-compounding scenarios wrong by a few percent. I checked.
• Auto loan amortization — same formula as mortgage but with shorter term assumptions; I sanity-check outputs against the standard payment tables in any consumer-finance textbook.

After I write a calculator, I work through three real scenarios by hand and confirm the output matches. If they disagree, I dig until I find which one is wrong. Sometimes it's me, and I fix it. Sometimes my reference source has a typo, and I escalate to a second source.

When I get something wrong — and I have — I want to know. The contact link below works. I read everything and I usually reply within a day or two.

The technology behind ToolCalcs

The whole site is static HTML. There's no database, no user accounts, no analytics tracking your every move. The calculations all run in your browser as JavaScript. When you load a page, you're downloading some HTML and JS, and that's it.

I built it on Astro because static site generators force you to be honest about what's actually on each page. There's no "loading…" spinner, no server-rendered template that secretly fetches from an API. What you see when you View Source is what's actually there.

It's hosted on Cloudflare Pages, which is free for sites my size. That's why I can keep this ad-light: I'm not paying $200/month for a server farm to host a glorified spreadsheet.

The downside: I can't do clever personalization. I can't remember your inputs across visits. I can't show you "your" mortgage rate. You're the same anonymous visitor I am. I think that's actually a feature, not a bug.

My research process for articles

When I write a guide — say, the 2026 Federal Tax Brackets piece — here's what happens, in order:

1. Find the canonical source. For tax content that's the Rev. Proc. from the IRS. For BMI it's WHO documentation. For mortgage industry data it's the CFPB or FRED. I don't write from secondary blog posts.
2. Cross-check with two more sources. I want to see three independent reputable sources agree on a number before I write it down. Disagreements get a footnote in my draft and I track which source I trusted and why.
3. Worked example. Every guide includes at least one concrete numeric example you can verify yourself. If I can't construct a clean worked example, the article isn't ready.
4. Update annually, or whenever the underlying rule changes. Tax brackets, contribution limits, FICA caps, mortgage conforming-loan limits — these change every year. Articles on the site carry publish dates and update dates for a reason.
5. Cite the source in the article. If I tell you the standard deduction in 2026 is $14,600 (single), I link to the IRS announcement that says so.

If you ever see a number on this site that contradicts the actual primary source, that's a bug. Tell me and I'll fix it. The corrections process is documented in our editorial standards.

Sources I rely on

The references I lean on most often, in case you want to verify anything yourself:

• IRS — irs.gov — tax brackets, contribution limits, withholding tables, Revenue Procedures
• CFPB — consumerfinance.gov — mortgage rules, consumer-finance regulation, complaints database
• FRED — fred.stlouisfed.org — historical interest rates, inflation series, the 30-year mortgage average (MORTGAGE30US)
• BLS — bls.gov — Consumer Price Index, wage data, employment cost index
• Federal Reserve — federalreserve.gov — federal funds rate, monetary policy
• SSA — ssa.gov — Social Security tax cap, retirement age, benefit formulas
• WHO — who.int — BMI categories, adult health metrics
• CDC — cdc.gov — calorie and activity guidelines, pediatric growth charts, pregnancy due-date math
• NIH — nih.gov — clinical references for the health calculators
• SEC — sec.gov — investment regulations, 401(k) and IRA rules
• Freddie Mac PMMS — for the historical mortgage-rate context used in the refinance calculators

What I care about

Getting the math right. Financial calculators that use wrong formulas are dangerous. When I build a mortgage calculator, I use the actual amortization formula — the same one your bank uses. When I write about tax brackets, I pull the numbers from IRS.gov, not from some blog that copied it from another blog. If I mess something up, I want to hear about it: contact@toolcalcs.com.

Not wasting your time. No sign-ups. No "enter your email to see results." No paywalls. You came here to calculate something — the answer should be two clicks away, not behind a lead-gen form.

Your privacy. Every calculation runs in your browser. I don't see your numbers. I don't store your data. I literally can't, because there's no server-side processing. The site is static HTML hosted on Cloudflare Pages.

What I'll never do

• Sell your data. There's nothing to sell because I don't collect it.
• Gate a calculator behind an email signup or "free trial."
• Show you a fake "limited-time" rate or fabricated countdown timer.
• Publish AI-generated content without reviewing every formula and worked example by hand.
• Pretend I'm a CPA, CFP, attorney, or physician. The disclaimers on this site aren't boilerplate — they're load-bearing.
• Add a "premium" tier. The whole point is that this stuff should be free.

What I'm not

I'm not a CPA. I'm not a Certified Financial Planner. I'm not a doctor. The BMI and calorie calculators are based on WHO formulas, but please talk to an actual physician about your health. The tax calculators reflect the published IRS rules, but they're not a substitute for advice from a CPA who knows your specific situation.

I'm a person who reads IRS publications for fun and thinks spreadsheets are underrated. The articles I write reflect my own research and understanding. When the topic is serious (taxes, retirement, insurance, major health decisions), I cite my sources and I'm upfront about what I don't know.

If you're making a major financial or medical decision — buying a house, choosing between an LLC and S-Corp, planning your retirement, interpreting test results — please talk to a professional. My calculators give you a starting point. They're not a substitute for advice from someone who knows your specific situation.

The tools

Here's what's on the site right now:

• Financial calculators — mortgage, compound interest, 401(k), tax, debt payoff, and about 30 more
• Health calculators — BMI, calories, TDEE, macros, pace, pregnancy due date
• Business tools — break-even, profit margin, payroll cost, LLC vs S-Corp
• Education — GPA, college cost, student-loan repayment, SAT scores
• Auto — car payment, depreciation, EV vs gas, fuel cost
• Printable worksheets — 95+ for Pre-K through 6th grade (math, reading, seasonal)
• Personality tests — MBTI, DISC, Enneagram, Big Five, and more
• Blog — 225 guides on personal finance, investing, taxes, and health

How I make money (or don't, yet)

Right now? I don't. This site costs me about $0/month to run (thanks, Cloudflare free tier) plus the domain registration. Eventually I'd like to add some non-intrusive ads to cover the time I put into it. But I'm not going to plaster ads everywhere or add a "premium" tier. The whole point is that this stuff should be free.

Get in touch

Found a bug? Think a formula is wrong? Have an idea for a calculator I should build? Email me at contact@toolcalcs.com. I read everything and I usually reply within a day or two.

You can also check out our editorial standards if you're curious about how I fact-check the financial content, the correction process, and the AI-content policy.