Skip to content
Calcumatix
en
enEnglishesEspañol
Free to Use, No Sign-Up

Calculate the Answer and Understand the Math Behind It

Calcumatix is a free calculator site covering math, health, finance, dates, and more, with new categories and calculators added over time. It's built for people who want to see how a number is worked out, not just the number. Every tool shows the formula in plain words and walks through a worked example, step by step, on tested math you can check yourself, with no account and no paywall.

Browse Calculators How We Test
  • 173 Free Calculators
  • Clear Formulas
  • Worked Examples
  • Tested Results
  • No Sign-Up

Popular Calculators

View All →

Solar Battery Calculator

Size your off-grid solar battery bank in amp-hours by entering your daily energy use, system voltage, autonomy days, and depth of discharge.

Open the Calculator

Fraction Calculator

Add, subtract, multiply, or divide two fractions and see the reduced answer, decimal form, and working steps.

Open the Calculator

BMI Calculator

Calculate Body Mass Index from height and weight, and see your World Health Organization weight category.

Open the Calculator

Average Calculator

Find mean, median, and range from a list of numbers so students, teachers, and data readers can check center, middle, and spread.

Open the Calculator

Percentage Calculator

Find a percent of a number, compare part to whole, or measure percent change with the formula, steps, and a worked example shown.

Open the Calculator

Loan Calculator

Check a fixed loan payment, total paid, and interest cost from the loan amount, rate, and term.

Open the Calculator

Date Duration Calculator

Find the time between two dates in years, months, days, total days, and weeks, with leap-year handling and a worked example.

Open the Calculator

BMR Calculator

Estimate basal metabolic rate from age, sex, height, and weight, with metric or imperial inputs and a visible Mifflin-St Jeor example.

Open the Calculator

Browse by Category

Math

Percentages, fractions, averages and everyday arithmetic.

45 calculators

Construction

Material quantities, coverage, and weight for building and landscaping projects.

42 calculators

Engineering

Electrical, mechanical, fluid, machining, and computing calculations.

32 calculators

Finance

Loans, interest, and investment growth.

16 calculators

Sports

Shooting, save, and hitting percentages from official stat formulas.

14 calculators

Science

Percent by weight, by volume, and dilution for lab calculations.

13 calculators

Time & Date

Age, durations, and the days between dates.

8 calculators

Health & Fitness

BMI, BMR, and daily calorie estimates.

3 calculators

Recently Added

Grams to Troy Ounces Calculator

Convert between grams and troy ounces in either direction using the exact factor 1 troy oz = 31.1034768 g. Used for gold, silver, platinum, and other precious metals.

Open the Calculator

Net Effective Rent Calculator

Find the true average monthly cost of a lease after spreading free-rent periods and concessions across the full lease term. Enter your lease details below.

Open the Calculator

Volumetric Flow Rate Calculator

Find volumetric flow rate or fluid velocity in a pipe using the Q = A × v identity from pipe inside diameter and the known value.

Open the Calculator

Animal Gestation Calculator

Estimate a due date for sheep, dog, or pig pregnancy from the breeding date and the species average gestation length.

Open the Calculator

How Every Calcumatix Calculator Works, Step By Step

Every tool here works the same way, so you always know where the answer came from. Learn one tool and you can read them all.

  1. 1

    Enter Your Values

    Type your numbers into the clearly labeled, mobile-friendly inputs, each marked with the unit it expects so nothing is ambiguous.

  2. 2

    Read the Result

    See the answer with a plain-language quick summary, the formula in words, and a full worked example laid out right beside it.

  3. 3

    Check and Trust It

    Follow the worked example with your own numbers, then read the assumptions, limits, and sources to see how far to trust it.

Why Calcumatix Calculators Are Built to Be Trusted

We earn trust by showing our work, not by asking for faith. That is the difference between a tool that explains and one that only prints a number.

Formula Shown in Plain Words

Every result comes with the formula behind it, from WHO BMI categories to the Mifflin-St Jeor and amortization formulas, written out so you can follow the math yourself.

Worked Example, Step By Step

A worked example shows each step and the rounding, so you can reproduce the result by hand and confirm it makes sense for your own numbers.

Tested Before It Goes Live

Each formula lives in its own module and is checked by an automated test suite covering normal values, edge cases, and rounding. A calculator is not published until its tests pass.

Named Sources for Health & Finance

Health and finance tools cite a named source, so you can see exactly where a formula comes from and check it against the original reference.

Transparent Assumptions & Limits

Short notes flag what a tool does not cover, such as fees, taxes, or individual variation, so you know exactly how far a result should be trusted.

No Account, No Data to Hand Over

Every calculator is free with no sign-up, no login, and no paywall. Calculations run right in your browser on any phone, tablet, or desktop.

Calculators by Topic

Jump straight to the tool you need, or open a category hub to see everything in that area.

Math Tools

All Math Calculators

Construction Tools

All Construction Calculators

Engineering Tools

All Engineering Calculators

Finance Tools

All Finance Calculators

Sports Tools

All Sports Calculators

Science Tools

All Science Calculators

Time & Date Tools

All Time & Date Calculators

Health & Fitness Tools

All Health & Fitness Calculators

Helpful Guides

Plain-language explainers on how the calculations work, so you understand the result, not just the number.

View All Guides →

How We Build Our Calculators

Learn how we select formulas, test calculations, round results, choose sources, and review each tool, so you know exactly what you are getting.

Read Our Methodology

Frequently Asked Questions

Are Calcumatix calculators free to use without limits?

Yes, every tool on the site is free, with no limit and no sign-up. You can run as many calculations as you need. There is no paid tier that hides the real answer.

Do I need an account to use a calculator?

No account is needed to use any tool here. You open the page, enter your values, and read the result. The formula and worked example sit right beside it, with nothing to register for.

How accurate are the calculations on Calcumatix?

We test each tool against its published formula before it goes live. Every result shows the formula and a worked example, so you can check the math yourself. The health and finance tools also cite a named source.

Which calculator categories does Calcumatix cover?

The site covers 8 groups: Math, Health & Fitness, Finance, Time & Date, Sports, Science, Construction, Engineering, with more calculators and categories added over time. Each group holds related tools in one place, so you can move from a broad question to the exact tool that answers it.