Calculators

About Calculators

A calculator is worth reaching for when the arithmetic is easy to get wrong rather than hard to do: a percentage change that inverts if you divide by the wrong figure, a loan payment that compounds monthly, a due date counted across leap years. The calculators here cover the four situations that come up most — money, grades, health, and time — and each shows the numbers it worked from, not just the answer, so you can check the result rather than trust it. Everything runs on your device: nothing you type is sent anywhere, which matters more than it sounds when the figures are your salary, your loan balance, or your weight.

Which one you want usually depends on what you already know. If you have a price and a rate, the discount and sales tax calculators go straight there. If you have a balance and a term, the loan and mortgage calculators give the monthly payment and the total interest — which is the number worth looking at, because a longer term almost always lowers the payment while raising what you eventually hand over. Compound interest runs the same maths in the direction you want it to go, and it is the clearest way to see why starting earlier beats saving more.

The health and grade calculators are the ones to read with the most care. BMI is a rough population measure that takes no account of muscle, frame, or age, and BMR is an estimate from a formula rather than a measurement of you. Both are useful as a starting point and misleading as a verdict. Grade and GPA results depend entirely on your institution's weighting, so check the scale you enter against the one you are actually marked on before you rely on the figure.