Online Calculators
Choose a category or pick a popular calculator. Most explain the formula behind the result and show a worked example, so you can check the answer instead of just trusting it.
24 popular calculators
Calculators by category
Math & Geometry18 calculatorsFinance & Business14 calculatorsHealth & Fitness11 calculatorsDate & Time8 calculatorsHome & Cooking6 calculatorsEveryday6 calculators
Math & Geometry calculators
- Percentage CalculatorPick the question you need answered, enter two numbers and get the result instantly, whether you want a percent change, a percentage difference or X% of Y.
- Area CalculatorChoose a shape, enter the measurements you know and get its area in the unit you prefer. Triangles can be solved from sides, angles, or a hypotenuse and a leg.
- Volume CalculatorPick a solid, enter its dimensions in whichever units you measured them in, and get the volume in the cubic unit you prefer. Boxes, cubes, cylinders, cones, spheres and triangular prisms are covered.
- Exponent CalculatorType a base and an exponent, whole, negative or fractional, and get the power straight away. A power with no real value, or one too large to store, is reported as such instead of as a wrong number.
Finance & Business calculators
- Compound Interest CalculatorEnter a starting balance, an interest rate and a term to see how money grows when interest is added to the balance. Add regular deposits or withdrawals to model a savings plan.
- Discount CalculatorChoose whether to apply a discount to a price or to find the discount between two prices. Pick the type of offer, enter the prices and see what you pay, what you save and the discount as a percentage.
- VAT CalculatorPick whether you are adding VAT to a price or removing it, enter the amount and the VAT rate, and see the price and the tax portion at once.
- APY CalculatorEnter the stated interest rate and how often it compounds to get the annual percentage yield. Add a starting balance and a term to see the interest it earns.
Health & Fitness calculators
- BMI CalculatorEnter your height and weight to see your body mass index, the weight category it falls into and how far you sit from the edges of the healthy range. BMI is a screening number for adults, not a diagnosis, and it says nothing about muscle or where fat is stored.
- Daily Water Intake CalculatorEnter your age, sex, height, weight and activity level to get a daily water target in milliliters, liters, ounces and cups, plus the share to drink as fluids. The target is built from your daily energy use at about 1 mL of water per kilocalorie.
- Calorie CalculatorEnter your age, sex, height, weight and activity level to see the daily calories that hold your weight steady, plus targets for losing or gaining about half a kilogram to a kilogram a week.
- 1-Rep Max CalculatorEnter the weight you lifted and how many clean reps you completed. The calculator estimates the heaviest single you could lift and lists the weights that correspond to common rep targets.
Date & Time calculators
- Hours CalculatorEnter a start time, an end time and an optional break to get the time in between as hours and minutes, decimal hours and total minutes. A second mode handles two full dates with times.
- Age CalculatorPick a starting point (a birth year, a full date of birth, or a known age) and the calculator works out the rest. With a full date you get an exact age down to the day.
- Days CalculatorUse the days calculator to find how many days lie between two dates, or to add days to a date and see the result with its day of the week. Weekdays, weeks and months are reported too.
- Sleep CalculatorEnter the time you need to wake up and get a bedtime that fits whole sleep cycles, or enter your bedtime and get matching wake-up times. Age group, time to fall asleep and cycle length are adjustable.
Home & Cooking calculators
- Coffee Ratio CalculatorChoose a brewing method and strength, then say how much coffee you want to make or how much ground coffee you have. The calculator returns the ratio and the matching weights of coffee and water in metric and US units.
- Concrete CalculatorChoose what you are pouring, enter its dimensions in any mix of units, and see how much concrete it takes as a volume, a weight and a bag count. Add a price and the same figures become a cost estimate.
- Paint CalculatorWork out how much paint a room or a house exterior needs. The calculator subtracts windows and doors from the wall area, multiplies by the number of coats and rounds up to whole gallons or liters.
- Recipe ScalerPaste your ingredients, enter the original and the new number of servings, and the scaler multiplies every amount for you. It can also switch the units between metric and US.
Everyday calculators
- Grade CalculatorThree tools in one: convert marks to a percentage and letter, combine graded work into a weighted course grade (with the score you need on the final), or see how a new grade would change your current average.
- Tip CalculatorEnter the bill, choose a tip percentage and, if you are sharing, the number of people. You get the total, the tip, and each person's share, with optional rounding up.
- Random Password GeneratorSet the length and the kinds of characters you want, then press the button for a fresh random password. Copy it into your password manager and use it for one account only.
- Final Grade CalculatorEnter your current grade, the grade you are aiming for and how much the final counts toward the course. The calculator tells you the minimum exam score that gets you there, or says so if it cannot be done.