Calculators
Dekuz's calculators handle everyday number problems: percentages, ratios, fractions, averages and quick number-theory checks like GCD and LCM. Each tool runs in your browser and links to closely related calculators, such as the Percentage Calculator, Fraction Calculator and Ratio Calculator, so you can move between related tasks without leaving the page.
Age Calculator
Calculate exact age in years, months and days between two dates.
%Percentage Calculator
Find a percentage of any number instantly.
BMIBMI Calculator
Estimate body mass index from height and weight.
FRACFraction Calculator
Add, subtract, multiply or divide two fractions and simplify the result.
RATIORatio Calculator
Simplify a two-number ratio and view its decimal relationship.
AVGAverage Calculator
Find the mean, sum, count, minimum and maximum of a list of numbers.
GCDGCD Calculator
Find the greatest common divisor of two integers.
LCMLCM Calculator
Find the least common multiple of two integers.
Δ%Percentage Change Calculator
Measure percentage increase or decrease from an old value to a new value.
PROPProportion Calculator
Solve a simple proportion in the form a/b = c/x.
√Square Root Calculator
Calculate the principal square root of a non-negative number.
POWExponent Calculator
Raise a base number to any numeric exponent.
MODModulo Calculator
Find the remainder after dividing one number by another.
GPAGPA Calculator
Calculate grade point average from letter grades and credit hours.
σStandard Deviation Calculator
Find the mean, variance and standard deviation of a list of numbers.
PRIMEPrime Number Checker
Check whether a number is prime and see its smallest factor.
ROMRoman Numeral Converter
Convert between numbers and Roman numerals in both directions.
CALCalorie Calculator
Estimate daily calories (BMR and TDEE) for maintaining, losing or gaining weight.
CGPACGPA to Percentage Calculator
Convert CGPA to percentage and back using the HEC Pakistan formula (4.0 and 5.0).
FUELFuel Average Calculator
Find your car or bike's km per litre, cost per km and plan trip fuel cost.
MARKSMarks Percentage Calculator
Add subject-wise marks to get your total, percentage and subjects below the pass mark.
What you will find in the Calculators category
This category collects the everyday number tools that people reach for in school, at work and at home. For comparing amounts you can use the Percentage Calculator, the Percentage Change Calculator, the Ratio Calculator and the Proportion Calculator. For working with fractions and whole numbers there are the Fraction Calculator, the GCD Calculator, the LCM Calculator, the Prime Number Checker and the Modulo Calculator. Powers and roots are covered by the Exponent Calculator and the Square Root Calculator, and the Roman Numeral Converter translates between ordinary numbers and Roman numerals. Statistics basics come from the Average Calculator and the Standard Deviation Calculator, and three personal tools, the Age Calculator, the BMI Calculator and the GPA Calculator, handle common questions about dates, health and school results. Every tool runs in your browser and explains its formula on its own page.
Choosing the right percentage tool
Percentages cause more confusion than almost any other topic, mainly because the same word is used for different questions. If you want to know what a share of a number is, such as 18 percent of 2,450, the percentage calculator is the right tool. If you want to know how much a value rose or fell, for example a rent moving from 1,200 to 1,296, use the percentage change calculator, which divides the difference by the old value. If you want to compare two quantities without a base, such as boys to girls in a class, the ratio calculator simplifies the relationship, and the proportion calculator finds a missing value when two ratios must match, for example scaling a recipe. Choosing the tool that matches the question prevents the most common error, which is dividing by the wrong number.
Whole numbers, factors and remainders
The number theory tools work well together. The greatest common divisor tells you the largest number that divides two values exactly, and the least common multiple tells you the smallest number that both divide into. Together they simplify fractions and combine them: to add 7/15 and 11/20, find the least common multiple of 15 and 20, which is 60, and to simplify 462/1071, divide both by their greatest common divisor, 21. The prime number checker explains whether a value has any divisors other than one and itself, which matters for factorisation, and the modulo calculator gives the remainder after division, which is the key to repeating cycles such as clock arithmetic and day-of-week calculations. If a problem involves sharing, grouping or repeating patterns, one of these four tools usually applies.
Averages and standard deviation
The average calculator reports the mean, sum, count, minimum and maximum of a list, and the standard deviation calculator reports how spread out the values are. Used together they describe a data set far better than a single number. Two classes can both average 70 on a test, but if one has a standard deviation of 5 and the other 15, the second has far more variation and a typical student in it is much less predictable. Remember to choose between the population and sample versions of standard deviation: use the sample version when your numbers are a subset of a larger group. Always look at the minimum and maximum too, since one mistyped value can change the mean substantially.
Personal calculators: age, BMI and GPA
The age calculator counts exact years, months and days between a birth date and any other date, which helps with school cut-off dates, eligibility rules and milestones. The BMI calculator turns height and weight into a body mass index, which is a screening figure for adults and not a diagnosis, and it does not apply to children or pregnant women. The GPA calculator weights grades by credit hours using a standard four point scale, though your school may use a different scale. These tools give quick estimates, and for anything official, such as a legal age, a medical decision or a transcript, you should rely on the official document or a professional. Each page explains the assumptions and limits of the calculation.
How to check any calculator's answer
A good habit is to test every result in at least one way before you rely on it. First, estimate with round numbers: 18 percent of 2,450 should be a little under a fifth of 2,450, so about 440. Second, reverse the calculation: if 441 is 18 percent of a number, dividing 441 by 0.18 should return 2,450. Third, check units and signs, since a negative value or a result far from your estimate usually points to an input mistake. Fourth, compare with a known example, such as the worked example shown on each tool page. These checks take seconds and catch the majority of typing errors, wrong units and misunderstood questions.
Common mistakes to avoid
Several errors appear again and again. People apply a percentage to the wrong base, for example finding a discount from the sale price instead of the original price. They add the denominators when adding fractions. They report a mean for data with a few extreme values, when the median would describe it better. They read a BMI as proof of health or ill health. They forget that a percentage rise followed by the same percentage fall does not return to the starting value. And they mix up the number of decimal places that the question needs with the number that the calculator shows. Each tool page lists the assumptions it makes, and reading them avoids most of these problems.
Using these tools for learning, and your privacy
Students and teachers can use the calculators to check homework, explore patterns and see worked examples, for instance by trying different inputs on the GCD and LCM tools to see how the two numbers relate. Because every tool runs inside your browser, the numbers you type are not sent to Dekuz and are not stored, so you can use them freely for personal or sensitive figures such as grades or health measurements. The tools are free, need no account and work on phones. If you find a result that looks wrong, or you want a calculator added, the contact page explains how to tell us, and every correction improves the tools for everyone who uses them.
Frequently asked questions about the calculators
Are the results exact? The tools use standard formulas and display rounded values, so they are accurate enough for study, planning and everyday decisions, but for official documents you should confirm figures against the official source. Why does the percentage change calculator give a different answer from my mental estimate? Percentage change divides by the old value, and people often divide by the new value by mistake. Can I use the BMI calculator for my child? No, children are assessed on age-specific growth charts, so ask a doctor. Which standard deviation should I choose? Use the population version when your list is the whole group, and the sample version when it is part of a larger group. Do the tools save my numbers? No, calculations run in your browser and nothing is stored.
A short glossary
The mean is the sum of values divided by their count, and the median is the middle value of a sorted list. A ratio compares two quantities, and a proportion states that two ratios are equal. A factor divides a number exactly, and a multiple is the result of multiplying a number by a whole number. A prime number has exactly two factors, one and itself. A remainder is what is left after division, and modulo is the operation that returns it. An exponent shows repeated multiplication, and a root reverses it. Standard deviation measures spread around the mean, and percentage change measures the relative difference between an old and a new value.
Getting started: a suggested path
If you are new to the category, start with the Percentage Calculator and the Fraction Calculator, which cover the most common school and daily needs. Next try the Average Calculator with a list of numbers that you know, such as your last five test scores. Then explore the number tools, entering two numbers into the GCD Calculator and the LCM Calculator to see how they relate. If you are curious about statistics, move on to the Standard Deviation Calculator. For personal questions use the Age Calculator, the BMI Calculator and the GPA Calculator. On each tool page, read the worked example and the section on common mistakes, which shows how to check an answer.