About The Handy Calculators

Free, instant calculators built and reviewed by a real person — no signup, no fluff, no popups.

Who's behind the site

The Handy Calculators is an independent project founded and edited by Larius — a software engineer, licensed North Carolina real estate broker (No. 248735) and investor, Deputy Appraiser for a Florida county assessor's office in the Commercial Real Estate Department, and former retailer. He lives in North Carolina and Florida. In his county role he negotiates settlement agreements with attorneys who represent property owners and defends property values at Value Adjustment Board (VAB) hearings when settlements are not reached.

Every calculator on the site was built or reviewed by Larius personally, using the same mix of real-estate, personal-finance, and engineering experience he applies in his day-to-day work.

Our mission

Most online calculators are buried under ads, slow to load, or hidden behind signups. We're building the opposite: clean, fast, mobile-friendly tools that just work — for everything from mortgage payments to 1031 exchanges to BMI and unit conversions.

What's inside

We currently offer more than 100 calculators across:

• Money — mortgage, refinance, car payment, loans, savings, compound interest, paycheck, sales tax, discounts, rent vs buy.
• Real estate — cap rate, cash-on-cash, 1031 exchange, closing costs, multifamily / hotel / retail / office / industrial proformas.
• Health — BMI, calorie/TDEE, BMR, body fat, water intake, sleep cycles, pregnancy due date, ovulation.
• Time — days until a date, age, work hours, time zones.
• Education — GPA, percentages, grade needed.
• Conversions — units, temperature, currency, cooking.
• Home — concrete, paint, tile, wallpaper, mulch & gravel.

And we add new ones every week. Got an idea? Request a calculator.

How we build and review every calculator

Each page follows the same four-step process, documented in our editorial policy: pick a standard textbook or regulatory formula, cross-check the output against at least one authoritative source and one well-known reference calculator, document the simplifying assumptions on the page itself, and write a plain-English explanation with a worked example. For financial pages we lean on IRS publications, CFPB consumer guidance, and Fannie Mae / Freddie Mac underwriting documentation. For health pages we use published peer-reviewed equations and cite them.

How we make money

The site is supported by display advertising (Google AdSense). We never charge for calculators, never gate features behind accounts, and never sell your data. All inputs are processed in your browser.

Accuracy

We use industry-standard formulas (Mifflin–St Jeor for calories, PMT amortization for loans, the Gregorian calendar for dates, etc.) and test them carefully. That said, every calculator is an estimate — always verify important figures with a qualified professional.

Get in touch

Questions, corrections, or partnership inquiries? Email Larius@thehandycalculators.com or visit our contact page.

How we decide what to build next

There are already thousands of calculator pages on the web, and most of them are the same three formulas wrapped in different advertising. We only build a tool when we can do at least one of three things better: implement a formula that the popular results get wrong or oversimplify, expose an assumption that other pages bury, or cover a calculation that genuinely has no good free option.

The commercial real estate proformas are the clearest example of the third case. Multifamily, hotel, retail, office, industrial, and self-storage underwriting models normally live inside paid platforms or in spreadsheets passed between analysts. Building them as free, no-signup pages was worth doing because the alternative for most people is a subscription or a borrowed spreadsheet with someone else's assumptions hard-coded into it.

Reader requests drive a large share of the queue. When several people ask for variations on the same calculation, that is usually a sign the existing options are not answering the real question. Anyone can add to that queue through the request a calculator page.

Our correction process

Every page carries a review date, and corrections take priority over new features. When a reader reports a discrepancy, we reproduce it with their exact inputs, check the formula against its authoritative source, and compare against at least one independent reference implementation before deciding whether the page or the expectation is wrong.

Most reported discrepancies turn out to be assumption mismatches rather than errors — a mortgage figure that excludes PMI, a calorie equation that uses Mifflin-St Jeor where another site uses Harris-Benedict, a date calculation that counts the first day differently. When that happens we usually respond by making the assumption explicit on the page, because an undocumented assumption is a defect even when the arithmetic is correct. When the math is genuinely wrong, we fix it and update the review date.

We would rather hear about a suspected error and find it was a misunderstanding than have a wrong number sit on the site unreported. Corrections go to Larius@thehandycalculators.com or through the contact page.

Independence and editorial boundaries

The site is funded entirely by display advertising. We do not sell direct placements, sponsored content, paid links, or guest posts, and we decline these requests as a standing policy. No advertiser sees a page before it publishes, and no advertiser has ever influenced which calculators exist or what they recommend.

There are no affiliate links to lenders, brokers, insurers, supplement companies, or software. This costs real revenue — mortgage and insurance affiliate programs are among the most lucrative on the web, and a lending comparison table would earn more than every ad on the site combined. We do not run them because a calculator that quietly steers you toward whichever lender pays best is not a calculator, and the value of these tools depends entirely on the output being the same one we would give a family member.

Advertising is clearly distinguishable from content, and the calculations themselves are never influenced by it. What data is and is not collected is set out in the privacy policy.

Privacy by architecture

Every calculator runs entirely in your browser using client-side JavaScript. Salary figures, mortgage balances, health measurements, and pregnancy dates are computed on your device and never transmitted to a server, because there is no server-side calculation endpoint to transmit them to. You can verify this by disconnecting from the network — the calculators keep working.

This was a deliberate architectural decision rather than a policy promise. Policies change and companies get acquired; a page that never sends the data anywhere cannot leak it, sell it, or hand it over. The trade-off is that we learn far less about how the tools are used than a server-side site would, which we consider a fair price.

Limitations we want you to know about

Every calculator here is an estimate built on simplifying assumptions, and the useful ones state those assumptions plainly. Tax tools do not know your full return. Mortgage tools do not know your lender's overlays or your county's exact millage. Health tools use population equations that carry roughly 10% individual variance in either direction. Real estate proformas reflect the inputs you supply, and the hardest part of underwriting is choosing those inputs, not running the math on them.

None of this is a reason to distrust the output — it is a reason to treat it as a well-constructed starting point rather than a final answer. For decisions with real money, health, or legal consequences attached, take the result to a professional who can see your complete situation. The full statement of what these tools are and are not is in our calculator disclaimer.

Citing this site

Teachers, journalists, students, and researchers are welcome to link to, quote, or cite any page here with attribution — no permission needed. If you need clarification on how a particular formula is implemented, or want a figure confirmed before publication, write in and we will respond.