Online Calculator

How to use the online calculator

Tap the keys, or just start typing — the calculator listens to your keyboard as soon as the page opens, so you do not need to click the display first. The big line shows what you have entered, and the line under it previews the answer while you type. Press = or Enter to finish. After that, typing a digit starts a new calculation, while typing an operator such as + or × carries on from the answer, which appears as Ans.

You can enter a whole expression at once, brackets and all, such as (1250 − 175) × 1.08, and fix a typo by clicking in the display and moving the cursor. Every finished calculation goes onto the History tape: tap an expression to edit it again, tap a result to use it in your next sum, or press Copy to paste the whole tape into a note or an email. The Share button creates a link that opens with your last calculation on screen.

Keyboard shortcuts

Copy and paste work as usual in the display. For square roots, sin, cos, logarithms and factorials, use the scientific calculator — although this one also understands them if you type them, for example sqrt(2).

How the % key works

The percent sign simply means “hundredths”: 15% is 15 × 0.01 = 0.15. The only special case is + and −, where, as on most handheld and phone calculators, the percentage is taken of the number in front of it — the way you add a tip or take off a discount:

Calculators do not all agree on %, so the Working panel spells out which rule was used. For taxes, see the sales tax calculator; for stacked discounts, the discount calculator.

Order of operations (PEMDAS)

When a calculation mixes operations, the calculator follows the conventional order taught in US schools, remembered as PEMDAS (“Please Excuse My Dear Aunt Sally”):

1. Parentheses (brackets) first, innermost first.
2. Exponents (powers such as 2^3).
3. Multiplication and Division, working from left to right.
4. Addition and Subtraction, working from left to right.

Worked example: 12 + 7 × 3 is 33, not 57. Multiplication comes first, 7 × 3 = 21, then 12 + 21 = 33. Multiplication and division share a rank, as do addition and subtraction, so each pair is done strictly left to right: 20 − 8 ÷ 4 × 2 is 8 ÷ 4 = 2, then 2 × 2 = 4, then 20 − 4 = 16. Type either one and the Working panel below the keypad lists the same steps in the same order. A cheap calculator that works through each key as you press it would give 57 for the first example — that is the most common reason two calculators disagree.

Memory keys

Memory is handy for totals built from several separate calculations. To add up three items bought in different quantities, type 3 × 4.25 and press M+, then 2 × 7.5 and M+, then 12.99 and M+. Press MR and the display shows the running total, 40.74. M− subtracts instead, and MC resets the memory to zero.

Why 0.1 + 0.2 shows 0.3 here

Computers store numbers in binary, and many everyday decimals — 0.1 among them — have no exact binary form, so raw computer arithmetic gives 0.1 + 0.2 = 0.30000000000000004. This calculator rounds every displayed answer to 12 significant digits and treats a sum that should cancel out as exactly zero, so you see 0.3, and 0.1 + 0.2 − 0.3 gives 0. The rounding is only in the display: the full value is kept for Ans, memory and the history, so 1 ÷ 3 followed by × 3 returns exactly 1.

Two honest limits: whole numbers above about 9 quadrillion (2⁵³) cannot be stored exactly, and repeating decimals such as ⅓ are approximations. If you need exact answers with fractions, use the fraction calculator, which works with whole-number arithmetic and never rounds.