Free Online Calculators
Each calculator answers one question with a known formula: a monthly loan payment, compound interest, sales tax, BMI, daily calories, a GPA, a percentage or a fraction. Numbers you enter are computed client-side and never stored.
Showing 18 tools
Percentage Calculator
Calculate percentages three ways - what is X% of Y, X is what percent of Y, and percentage increase or decrease between two numbers.
Age Calculator
Calculate exact age in years, months, and days from a date of birth - plus total months, weeks, days, hours, and minutes, the weekday you were born, and a countdown to your next birthday.
Loan / EMI Calculator
Calculate your monthly loan payment (EMI), total interest, and payoff date, with a full amortization schedule and extra-payment savings.
Aspect Ratio Calculator
Calculate the missing width or height for any aspect ratio, simplify a size to its ratio, and scale images or video without distortion.
BMI Calculator
Calculate Body Mass Index from weight and height in metric or imperial units, with the WHO category, your healthy weight range, and the exact formula.
Tip Calculator
Calculate the tip and split the bill between any number of people, with sales tax, tip-on-pre-tax, and round-up options.
Discount Calculator
Work out the sale price and money saved from a percentage or fixed discount, stack an extra coupon, and add sales tax - with the effective discount shown.
Compound Interest Calculator
Project how savings and investments grow with compound interest - set the rate, term, compounding frequency, and recurring contributions to see the future value, interest earned, and a year-by-year breakdown.
TDEE Calculator
Calculate your Total Daily Energy Expenditure and BMR with the Mifflin-St Jeor equation, plus calorie targets and a macro split for any goal
Fraction Calculator
Add, subtract, multiply, and divide fractions online - with whole numbers, mixed numbers, and decimals, reduced to lowest terms with step-by-step working
GPA Calculator
Calculate your GPA from letter grades and credit hours on the 4.0 scale, with weighted Honors and AP/IB options and a running cumulative GPA.
Average Calculator
Calculate the mean, median, mode, range, and standard deviation of any list of numbers. Paste comma, space, or line-separated values and get every summary statistic at once.
Pace Calculator
Calculate running pace, finish time, or distance from any two values, with speed and per-kilometre or per-mile splits.
Profit Margin Calculator
Calculate gross profit margin, markup, and selling price from cost and revenue. Solve for price from a target margin and see margin versus markup side by side.
Sales Tax Calculator
Add sales tax to a price or back it out of a tax-inclusive total. Works for any rate, shows the net, tax, and gross amounts, and multiplies by quantity.
Ratio Calculator
Simplify a ratio to its lowest terms and solve proportions. Reduce values like 1920:1080 to 16:9, or find the missing number in A:B = C:D, with decimals and percentages, all in your browser.
Grade Calculator
Calculate a weighted course grade from assignment scores, or work out the score you need on the final exam to hit your target grade.
Standard Deviation Calculator
Calculate population and sample standard deviation, variance, mean, median, mode, and range from any list of numbers.
An online calculator answers a question that has one right number and a formula nobody memorises. The free online calculators here fall into four groups: money, where the arithmetic compounds and small inputs move large outputs; body metrics, where the formula is a population estimate rather than a measurement of you; school marks; and the everyday arithmetic that is faster to type into a purpose-built field than into a general calculator.
The money tools are the ones worth being careful with. The loan and EMI calculator produces a monthly payment and the full amortisation schedule behind it, which is the only way to see how little of an early payment touches the principal. The compound interest calculator shows the same effect from the other side, and lets you set how often interest compounds, because annual and monthly compounding on the same rate do not give the same answer. The sales tax calculator adds a rate to a price or backs it out of a tax-inclusive total, the same reverse-percentage arithmetic that trips people up when they try to subtract a percentage off a receipt. Anything measured in days rather than money is in time and date, and unit arithmetic, metric to imperial and one time zone to the next, is in converters. A figure worked out from a birth date rather than from a sum is an astrology calculator instead.
What each calculator works out, and what it needs from you
| Calculator | You supply | You get |
|---|---|---|
| Loan / EMI | Amount, rate, term | Monthly payment, total interest, amortisation schedule |
| Compound Interest | Principal, rate, term, frequency | Final balance and interest earned |
| Discount | Price and percentage off | Sale price and the amount saved |
| Sales Tax / VAT | Amount, rate, add or remove | Net, tax and gross totals |
| Tip | Bill, tip percentage, party size | Tip, total, and per-person split |
| Percentage | Any two of three values | Percent of, percent change, or what percent |
| BMI | Height and weight | BMI and its WHO category |
| TDEE | Age, sex, height, weight, activity | BMR, maintenance calories, macro split |
| Age | Birth date, optional target date | Age in years, months, days |
| GPA | Grades and credit hours | Weighted grade point average |
| Grade | Scores and their weights | Weighted course grade, letter, and score needed on the final |
| Average | A list of numbers | Mean, median, mode and range |
| Standard Deviation | A list of numbers | Population and sample SD, variance, mean, median, mode |
| Fraction | Two fractions and an operator | Simplified result, as a fraction and a decimal |
| Aspect Ratio | A width or a height, and a ratio | The matching dimension |
| Profit Margin | Cost and revenue, or either plus a margin | Gross margin, markup, and the price that hits it |
| Pace | Any two of pace, distance and time | The third, in pace and in speed |
Where the money calculators surprise people
The monthly payment on a loan is the number everyone asks for and the least informative one. What the amortisation schedule shows is that early payments are almost entirely interest: on a 25-year mortgage, the first payment can put under a fifth of itself against the principal, and the ratio only crosses halfway years in. This is also why an overpayment is worth so much more than its size suggests, since it comes off the principal directly and removes every future month of interest that principal would have earned. The loan calculator models an extra payment for exactly this reason.
Compounding frequency is the other quiet variable. The same nominal rate compounded monthly rather than annually produces a higher effective rate, which is why lenders quote one and savings accounts advertise the other. Over a year the gap is small; over thirty it is not, and the difference is entirely in a dropdown most calculators do not offer. If you want the effect in a single sentence: interest on interest is the whole product, and frequency decides how often it starts.
The body calculators are estimates, and say so
BMI is weight divided by height squared, and the World Health Organization bands it at 18.5, 25 and 30. It was designed by a statistician to describe populations, not individuals, and it does not know the difference between muscle and fat: a heavily trained athlete lands in the overweight band routinely. The bands also fit some ancestries poorly, which is why several health bodies use lower thresholds for South and East Asian populations. Read it as one number among several rather than a verdict.
The TDEE calculator uses the Mifflin-St Jeor equation, which research has found to be the most accurate of the common predictive formulas, and multiplies the resulting BMR by an activity factor between 1.2 and 1.9. The activity factor is where the error lives: most people place themselves a band too high, and the difference between two adjacent bands is a few hundred calories a day. Treat the output as a starting point to be corrected by what the scale does over three or four weeks, not as a measured quantity.
The everyday arithmetic
The word percentage covers three different questions, and confusing them is the single most common arithmetic error in ordinary use. What is 15% of 80, what percent is 12 of 80, and what is the change from 80 to 92 all have different formulas and all get called a percentage calculation. The percentage calculator puts the three side by side rather than making you decide which one you are asking. The same distinction matters in reporting: a rate moving from 3% to 5% has risen 2 percentage points and 67 percent, and both numbers are correct.
Elsewhere the value is in the input format rather than the arithmetic. The fraction calculator simplifies as it goes, so you never see 84/144 as an answer. The age calculator does the calendar arithmetic that trips people up around leap days and month lengths. The aspect ratio calculator turns one known dimension into the other, which is the daily arithmetic of anyone laying out images or video. Two more solve for whichever value you are missing: the profit margin calculator works backwards from a target margin to a selling price, and the running pace calculator gives you the third of pace, distance and time from any two. Everything runs client-side: nothing you enter, including salary, loan amount or body measurements, is sent anywhere.
School marks and the spread of a data set
Grades are almost never a plain average, because a syllabus weights homework, quizzes and exams differently. The grade calculator combines weighted scores into one course grade with its letter, and its final-grade mode answers the question every student types in December: what score do I need on the final to reach my target? It also tells you when the target is already secured or already out of reach, which the GPA calculator does not, since GPA works from letter grades and credit hours across whole courses rather than assignments within one.
Once you have a list of numbers, the average is only half the story. The average calculator gives the mean, median and mode; the standard deviation calculator adds the piece that tells you how spread out those numbers are, in both the population and the sample form. The distinction matters more than it looks: dividing by N describes a complete group, while dividing by N minus 1 estimates a larger population from a sample, and the two give different answers on the same data. Two classes can share an average of 75 and be entirely different groups, which is exactly what the standard deviation reveals.
Frequently asked questions
Are the numbers I enter into these calculators stored?
No. Every calculator here runs client-side, in your browser, and computes from the values in the form without sending them anywhere. That matters more than usual for this category, since the inputs are salaries, loan balances, body weights and grades, all of which are ordinarily typed into a form that posts them to a server.
Is EMI the same as a monthly loan payment?
Yes. EMI stands for Equated Monthly Instalment, the term used across South Asia for the fixed monthly payment on an amortising loan, and it is the same figure a mortgage or car loan calculator elsewhere calls the monthly payment. The split between interest and principal inside that fixed amount changes every month, which is what the amortisation schedule shows.
How much does making extra loan payments save?
More than the size of the payment suggests, because an overpayment reduces the principal directly and cancels all the future interest that principal would have accrued. The saving is largest early in the term, when almost all of a scheduled payment is interest. The loan calculator shows the revised payoff date and total interest alongside the original.
How accurate is a BMI calculation?
The arithmetic is exact and the interpretation is not. BMI is weight over height squared, a population measure that cannot distinguish muscle from fat, so muscular people are routinely classed as overweight. The WHO thresholds of 18.5, 25 and 30 also fit some ancestries poorly, and several health bodies apply lower cut-offs for South and East Asian populations.
Which formula does the TDEE calculator use?
Mifflin-St Jeor for basal metabolic rate, multiplied by an activity factor from 1.2 for sedentary up to 1.9 for very heavy training. Mifflin-St Jeor is generally the most accurate of the common predictive equations, but every one of them is a population estimate, so use the result as a starting point and adjust from three or four weeks of real data.
What is the difference between a percentage and a percentage point?
A percentage point is an absolute difference between two percentages; a percentage is a relative one. A rate rising from 3% to 5% has risen 2 percentage points, and also risen about 67 percent. Both are true, which is why the two are so often mixed up in reporting, and why the percentage calculator labels which question it is answering.