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KalkoroFree online calculators
Percentages, BMI, loan payments, dates, unit conversions and more: every calculator shows the formula, a worked example and its sources. No sign-up, nothing to install.
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- 134
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- languages
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Each category keeps its calculators, reference tables and guides together.
Method
How Kalkoro keeps calculations right
A calculator is only as good as its answer. Every Kalkoro tool ships under four rules.
Sourced formulas and values
Formulas and reference values come from primary sources such as NIST, the CDC, the WHO and the original studies. Each page lists the sources it relies on, so you can check them yourself.
Step-by-step solutions
We don’t just print a number. Every calculator page shows the formula, the same formula with the numbers filled in, and a charted worked example.
Your numbers stay on your device
All calculations run in your browser. The values you enter are never sent to our servers, and every tool works fully without an account.
Written and reviewed by editors
Each calculator is prepared by one editor and checked by a second. Formulas are covered by automated tests, and every reported error is reviewed by an editor.
Fresh
Recently updated calculators
Guides
Calculation guides
- How to calculate a percentageFrom finding the percentage of a number to percentage increase and decrease — the four questions, formulas and worked examples.
- Sample vs. population standard deviation: which one to useThe two formulas differ by just one number in the denominator (n vs. n−1) — but picking the wrong one systematically biases your result.
- How loan payments are calculatedThe amortization (annuity) formula behind every fixed monthly payment, with a fully worked $10,000 example.
- Understanding your BMIWhat body mass index measures, the WHO categories, the healthy weight range, and what BMI does and doesn't tell you.
Mobile app
Kalkoro in your pocket
The same calculators and the same sourced formulas: the Kalkoro app is free on iPhone and Android.
- Your favorite calculators one tap away
- Recent calculations synced across devices
- The same calculation engines as the website
Good to know
Frequently asked questions about Kalkoro
What is Kalkoro?
Kalkoro (kalkoro.com) is a free platform that brings hundreds of calculators together in one place: math, health, finance, dates, unit conversions and everyday tools. The website and the mobile app run on the same calculation engines.
Is Kalkoro free? Do I need an account?
Every calculator is free and works without an account. Signing up is optional; if you do, your favorites and your last 50 calculations sync across your devices.
Are the numbers I enter stored anywhere?
No. Calculations run on your device and the values you enter are not sent to our servers. Only if you create an account and choose to sync your history are your own calculation records kept in your account, and you can delete them at any time.
How accurate are the calculators?
Each calculator implements a published formula, is covered by automated tests with known-good values, and is reviewed by a second editor. Every page shows the formula and a worked example so you can verify the result. Health and finance results are informational, not professional advice.
Is there a Kalkoro mobile app?
Yes. Kalkoro is available for free on the App Store and Google Play, with the same calculators as the website.
What should I do if I find a mistake?
Use the “Report an issue” button on any calculator page, or write to us from the contact page. Reports are reviewed by our editors and confirmed errors are fixed and published.
Can I embed a Kalkoro calculator on my site?
Yes. Every calculator page has an “Add this tool to your site” box: copy the code and paste it into your page. The embedded calculator is free to use.
Which languages is Kalkoro available in?
English, Spanish and Turkish. Each language has its own catalog, built for the needs of its readers rather than translated word for word.
What is Kalkoro?
Kalkoro is a free platform of online calculators for everyday questions: percentages, averages and fractions; BMI, calories and due dates; loan payments, compound interest and tips; date differences, time cards and unit conversions from millimetres to inches or kilograms to pounds. Every calculator gives a clear answer in seconds, in a clean interface.
What sets Kalkoro apart from a plain calculator is its method. Formulas and reference values are taken from primary sources and listed on the page; each calculator shows how the result is reached, with the formula and a charted worked example; and every tool is checked by a second editor and by automated tests before it goes live.
Kalkoro is published in English, Spanish and Turkish, with a separate catalog for each language. Calculations run on your device and no account is required.