Free, fast calculators for everyday decisions

Who we are

Calc Hives is an independent website that publishes free online calculators and unit converters. What began as a small set of financial tools has grown into a broad collection spanning personal finance, fitness and health, mathematics and statistics, dates and time, academics, and engineering-style unit conversions for force, pressure, torque, length, area, volume, and weight.

Our goal is simple: help you get an accurate answer in seconds. Every tool is designed to run entirely in your browser, load quickly on any device, and explain the maths behind the result so you understand not just the "what" but the "why".

What we offer

Our library is organised into categories so you can find the right tool quickly:

• Financial calculators — mortgages, loans, auto and student loans, compound interest, investments, retirement, and income tax estimates.
• Fitness & health calculators — BMI, calories and TDEE, body fat, BMR, macros, plus pregnancy, ovulation, and due-date tools.
• Math calculators — a scientific calculator, fractions, percentages, standard deviation, triangles, and a random number generator.
• Everyday tools — age, date, time, hours, GPA, grade, concrete, subnet, a password generator, and a unit converter.
• Force, pressure & torque converters — Nm, ft-lbs, in-lbs, PSI, bar, torr, torque-to-horsepower, and more.
• Length & area converters — feet, inches, acres, hectares, plus astronomical units and light years.
• Volume & weight converters — gallons, litres, cups, grams, ounces, pounds, and density-based conversions.

How our calculators work

Each calculator uses well-established, publicly documented formulas — for example, the amortization formula for mortgages, the Mifflin-St Jeor equation for basal metabolic rate, and standard SI conversion factors for units. Wherever it helps, we show the formula, a worked example, and a short explanation so you can check the logic yourself.

All calculations happen locally in your browser. We do not store the numbers you enter, and your inputs are never sent to a server. That means your salary, weight, health details, or any figure you type stays on your device.

Accuracy and our commitment to quality

We take accuracy seriously and test our tools against known reference values. That said, calculators rely on the inputs you provide and on general assumptions that may not fit every situation. Results are estimates intended for planning and education, and they should not replace advice from a qualified professional such as a lender, financial advisor, accountant, doctor, or engineer.

If you ever find a result that looks wrong, please tell us. Feedback from people who use the tools every day is the single best way we improve them.

Who we build for

Our audience is everyone: students checking a GPA, families planning a home purchase, people managing their health, tradespeople estimating materials, and professionals who just need a quick, reliable conversion. Because of that range, we prioritise plain language, mobile-friendly layouts, fast load times, and accessibility.

Get in touch

Have an idea for a new calculator, spotted an error, or want to share feedback? We would love to hear from you. Visit our Contact Us page and send a message — we read every one.