About CalcMate

CalcMate is a collection of free online calculators built around one idea: when you need a quick answer, you should get it immediately — without popups, signups, or wading through paragraphs of filler to find the tool.

How the tools work

Every calculator on this site runs entirely in your browser. When you type a date or a number, the calculation happens on your device using JavaScript — nothing is transmitted to a server, logged, or stored. That is also why the tools feel instant: there is no round-trip to wait for.

Accuracy

Each tool documents the exact method and formula it uses, and edge cases (leap years, month lengths, zero denominators) are handled explicitly. If you ever get a result that looks wrong, please tell us — reports like that are how the tools improve.

Current tools

• Age Calculator — Calculate your exact age in years, months, and days from your date of birth. Also shows total days lived and a countdown to your next birthday.
• Date Difference Calculator — Count the days, weeks, months, and years between any two dates. Perfect for deadlines, anniversaries, project timelines, and countdowns.
• Percentage Calculator — Work out percentages instantly: what is X% of Y, X is what percent of Y, and percentage increase or decrease between two numbers.
• BMI Calculator — Calculate your Body Mass Index from height and weight in metric or imperial units, see your WHO weight category, and the healthy weight range for your height.
• Tip Calculator — Work out the tip and total for any bill, split it between any number of people, and round the total up or down to a clean amount.
• Discount Calculator — Find the sale price and money saved from a percentage discount, stack a second discount, and see the effective total percentage off.
• Loan Calculator — Calculate the monthly payment, total interest, and total cost of a loan or mortgage from the amount, annual interest rate, and term.
• Compound Interest Calculator — See how savings or investments grow over time with compound interest and optional regular contributions, at any compounding frequency.
• Calorie Calculator — Estimate your daily calorie needs (TDEE) from age, sex, height, weight, and activity level using the Mifflin-St Jeor equation, with targets for losing or gaining weight.
• Sales Tax Calculator — Add sales tax to a price to get the tax amount and total, or work backwards from a tax-inclusive total to find the pre-tax price and tax paid.
• Salary Calculator — Convert pay between hourly, daily, weekly, monthly, and annual amounts based on your hours per week and weeks worked per year.
• GPA Calculator — Calculate your weighted grade point average on a 4.0 scale from your course grades and credit hours, with each course counted by its weight.
• Pregnancy Due Date Calculator — Estimate your pregnancy due date from your last menstrual period using Naegele’s rule, adjusted for your cycle length, plus how many weeks along you are.
• Hours Calculator — Work out the time between a start and end time, subtract an unpaid break, and get the duration in hours and minutes and as a decimal for timesheets.
• Pace Calculator — Calculate your running pace per kilometre or mile from distance and time, and see your average speed for training and race planning.
• Temperature Converter — Convert temperatures instantly between Celsius, Fahrenheit, and Kelvin, with the exact conversion formulas shown for each pair.
• Ideal Weight Calculator — Estimate your ideal body weight from height and sex using the Robinson, Devine, Miller, and Hamwi formulas, plus the healthy weight range for your height.
• Body Fat Calculator — Estimate your body fat percentage with the U.S. Navy method from a few tape measurements, and see your body fat category and fat mass.
• ROI Calculator — Calculate return on investment as a percentage from your cost and final value, plus the annualized return when you enter a holding period.
• Fuel Cost Calculator — Work out the fuel cost of a trip from the distance, your vehicle’s fuel economy, and the price of fuel, in metric or imperial units.
• Mortgage Calculator — Estimate your full monthly mortgage payment from the home price, down payment, interest rate, and term — including property tax and home insurance.
• Savings Goal Calculator — Find out how much you need to save each month to reach a savings goal by a target date, taking your starting balance and interest into account.
• Length Converter — Convert lengths and distances between millimetres, centimetres, metres, kilometres, inches, feet, yards, and miles instantly.
• Ovulation Calculator — Estimate your most fertile days, ovulation date, and next period from the first day of your last period and your average cycle length.
• Weight Converter — Convert weight and mass between milligrams, grams, kilograms, ounces, pounds, and stones instantly, with every unit shown at once.
• Calories Burned Calculator — Estimate the calories you burn during exercise from your body weight, the activity, and how long you do it, using MET values.
• Simple Interest Calculator — Calculate simple interest and the total amount from a principal, annual interest rate, and time period, with the exact formula shown.
• Markup Calculator — Work out selling price, profit, and profit margin from a cost and a markup percentage — and see the difference between markup and margin.
• Speed Converter — Convert speed between kilometres per hour, miles per hour, metres per second, feet per second, and knots instantly.

New calculators are added regularly based on what visitors ask for.