Calculator – Free Online Basic Calculator

What is a calculator?

A calculator is a device or program that does arithmetic. This free online calculator adds, subtracts, multiplies, and divides numbers and shows the result on screen after each step.

How to Use the Calculator

1. Enter a number with the digit buttons 0 through 9.
2. Press an operator: + for addition, − for subtraction, × for multiplication, or ÷ for division.
3. Enter the second number.
4. Press = to see the result.
5. Press Clear to start over, or Backspace to remove the last digit.
6. Press the copy icon next to the display to copy the result.

Addition, Subtraction, Multiplication, and Division Formulas

The calculator uses four basic formulas, where a is the first number entered and b is the second:

• Addition: a + b
• Subtraction: a − b
• Multiplication: a × b
• Division: a ÷ b, where b cannot be 0

How the Calculator Handles Several Operations in a Row

This is a four-function calculator. It calculates each step as soon as the next operator is pressed, working through the numbers in the order they were entered. It does not follow the standard order of operations (also called PEMDAS or BODMAS), the rule that multiplication and division happen before addition and subtraction.

For example, entering 10 + 2 × 3 gives different answers depending on the method used:

• Order of operations: 10 + (2 × 3) = 16
• Step-by-step calculation, as this calculator does it: (10 + 2) × 3 = 36

The calculator shows 36. It adds 10 and 2 first, because × was pressed after that addition was already pending, then multiplies the running total by 3. Many simple pocket calculators work this way. Scientific and graphing calculators usually follow the order of operations instead.

Pressing an operator button twice in a row replaces the first choice with the second. For example, pressing 5, +, ×, 3, = calculates 5 × 3, which is 15, not 5 + 3.

Worked example

Addition: 47 + 28 = 75.

Division: 90 ÷ 4 = 22.5.

Step-by-step calculation with two operators: 4 + 6 × 2 = 20. The calculator adds 4 and 6 first, for 10, then multiplies by 2. It does not compute 4 + (6 × 2), which would equal 16.

Rounding and Number Display

Results are rounded for display to 12 significant digits. This hides small rounding errors that come from how computers store decimal numbers, so 0.1 + 0.2 displays as 0.3 instead of 0.30000000000000004. Numbers of 1 trillion or more, and numbers smaller than 0.000001, are shown in scientific notation, such as 1.5e+15. Rounding changes only what you see. The calculator keeps the unrounded result and uses it for the next step, so nothing is lost when you carry on calculating.

Dividing by Zero

Division by zero has no defined answer in arithmetic, so the calculator does not attempt it. Trying, for example, 8 ÷ 0 makes the display show "Cannot divide by zero." The calculator stays in this state until a new digit is entered or Clear is pressed.

Frequently asked questions

What operations can the calculator perform?

It performs addition, subtraction, multiplication, and division.

Does the calculator follow the order of operations?

No. It works through button presses in the order they happen, known as step-by-step or chain calculation, rather than by mathematical order of operations.

What happens if I divide by zero?

The display shows "Cannot divide by zero." Enter a new number or press Clear to continue.

Can I use decimal numbers?

Yes. Press the decimal point button to add a decimal point to the number being entered.

How precise are the results?

Results are shown to 12 significant digits. The calculator works with more digits than it shows, and it passes the full result on to the next step. That is why dividing 1 by 3 and then multiplying by 3 gives exactly 1. Very large or very small numbers switch to scientific notation.

Does the calculator support keyboard input?

No. Numbers and operators are entered by clicking or tapping the on-screen buttons.