These free online calculators give instant answers for percentages, age, BMI, loan payments, discounts, GPA, date differences and unit conversions. Every calculator is free, needs no sign-up, and works on phones and computers.
Calorie Calculator (Maintenance, Weight Loss & Gain)
Estimate how many calories you burn a day and how many to eat to maintain, lose or gain weight. US or metric units.Compound Interest Calculator
See how savings grow with compound interest and monthly contributions, with a year-by-year table.GPA Calculator (GPA and CGPA)
Calculate your semester GPA and cumulative CGPA from grades and credit hours — 4.0 scale, weighted Honors/AP, or your own grade points.Grade Calculator (Weighted Grade & Final Exam)
Work out your weighted class grade and letter grade, and find the score you need on the final exam to reach your goal.GST & Tax Calculator (Add or Remove GST/VAT)
Add or remove GST, VAT or sales tax at any rate, split CGST and SGST, and total several items like an invoice.Mortgage Calculator (with Taxes, Insurance & PMI)
Estimate your monthly mortgage payment with taxes, insurance, PMI and HOA, see total interest and payoff date, and test extra payments. Any currency.Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers (1–3,999), with a step-by-step breakdown.Sales Tax Calculator (US States, Add or Remove Tax)
Add sales tax to a price or take it out of a total. Pick a US state for an average rate or type your exact local rate.Tip Calculator (Split the Bill)
Work out the tip and total for any bill and split it between friends. Pick 10–25% in one tap or type your own.Working Hours Calculator (Timesheet with Overtime)
Add up a week of shifts with breaks and overnight hours, see total and overtime hours, and estimate pay. Export a CSV timesheet.Percentage Calculator
Work out percentages, percentage change and what percent one number is of another.Age Calculator
Calculate exact age in years, months and days, and the days until the next birthday.BMI Calculator
Calculate Body Mass Index in metric or imperial units, with the WHO category.Loan EMI Calculator
Calculate monthly loan instalments, total interest and a repayment schedule.Discount Calculator
Find the sale price and the amount saved from a price and discount percentage.Date Difference Calculator
Count the days, weeks and months between two dates, or add days to a date.Unit Converter
Convert length, weight, temperature, area, volume, speed and data units.
Calculator guides
- How to Calculate Hours Worked (With Breaks and Overtime)
- How to Calculate GPA and CGPA: Step-by-Step With Examples
- Roman Numerals: How to Read and Write Them (1 to 3,999)
- How to Calculate Age From Date of Birth in Years, Months and Days
- Loan EMI Formula: How to Calculate EMI With a Worked Example
- How to Calculate Percentages: Simple Formulas With Examples
About Calculators — guide, tips & FAQ
On this page
Which calculator do you need?
Money and shopping
- Loan Calculator: estimate a monthly payment and the total interest on a loan.
- Discount Calculator: see the sale price and how much you save.
- Percentage Calculator: work out a percentage of a number, a percentage change, or what percent one number is of another.
Dates and time
- Age Calculator: find an exact age in years, months and days.
- Date Difference Calculator: count the days between two dates.
School, health and conversions
- GPA Calculator: calculate a grade point average from course grades and credits.
- BMI Calculator: calculate body mass index from height and weight.
- Unit Converter: convert length, weight, temperature and other units.
- Roman Numeral Converter: convert numbers to Roman numerals and back.
Why use these online calculators?
A phone calculator can add and multiply, but it cannot remember a formula for you. Each tool here has the formula built in, labels every field, and shows the result in plain words, so you avoid the most common mistakes, such as dividing by the wrong number when you work out a percentage change.
The pages load quickly, need no app or account, and work the same on a phone, tablet or laptop.
Results appear straight away, and you can change one number at a time to see how it affects the answer. That makes it easy to test a bigger deposit, a shorter term or a different grade before you decide.
How to use the calculators
- Choose a calculator from the grid above, or search for it by name.
- Enter your numbers or dates.
- Read the result, which updates as you type or when you press Calculate.
- Change any value to compare different scenarios.
Getting accurate results
Check the units before you start. Mixing centimetres and inches, or a yearly and a monthly interest rate, is the most common cause of a wrong answer.
Loan results are estimates. Your lender may add fees, insurance or a different compounding method, so treat the figure as a guide and confirm the final numbers with the lender before you sign anything.
BMI is a quick screening measure, not a diagnosis. It does not account for muscle mass, age or body shape, so talk to a doctor if you have questions about your health.
The Unit Converter uses standard conversion factors. If you want to know how units like the metre and kilogram are defined, see the NIST guide to SI units.
Everyday examples
Planning a purchase? Use the Discount Calculator to compare two sale offers, then the Loan Calculator to see what monthly payment you can afford. Filling in a form that asks for your age on a specific date? The Age Calculator handles leap years for you. Counting down to an exam or a deadline? The Date Difference Calculator tells you exactly how many days are left.
About these free Calculators
Quick answers for everyday maths, health and money questions: percentages, exact age, BMI, loan EMIs, discounts, days between dates and unit conversions. Results update as you type.
Helpful guides
Frequently asked questions
Are the calculators accurate?
Yes. They use standard formulas; financial results are estimates, so confirm with your lender.
Do the calculators work on mobile?
Yes. Every calculator is fully responsive.
Is any data stored?
No. Calculations run in your browser.