Basic calculator guide
Use the keypad to enter a number, choose an operation, enter the next number, and press equals. The calculator works on phones, tablets, and desktop browsers.
It includes the four arithmetic operations, a percent key, sign toggle, decimal entry, delete, and clear for quick everyday calculations.
How to use the basic calculator
- Enter a number: Tap digits and use the decimal key when needed.
- Choose an operation: Select plus, minus, multiply, or divide.
- Complete the calculation: Enter the second number and press equals.
- Correct entries: Use DEL to remove the last digit or AC/C to clear.
Formula and variables
Choose the operation that matches the calculation you need. Division by zero is reported as an error.
a + b, a - b, a × b, or a ÷ b- a — First number
- The first value in the calculation.
- b — Second number
- The value added, subtracted, multiplied, or divided.
Everyday arithmetic
Add two shopping amounts and divide the total between four people.
- Amounts
- $12.50 + $8.75
- People
- 4
- 12.50 + 8.75 = 21.25
- 21.25 ÷ 4 = 5.3125
Result: $5.3125 per person
Round the displayed result to the precision appropriate for money.
Understanding your results
Read the result
Results are formatted for readability while retaining useful decimal precision. An Error display indicates an invalid operation such as division by zero.
Assumptions
- Operations are evaluated in the order entered.
- Displayed values are rounded for readability.
- The percent key converts the displayed number to a decimal by dividing by 100.
Limitations
- This is a four-function calculator and does not evaluate full order-of-operations expressions.
- For trigonometry, roots, logarithms, or advanced formulas, use a scientific calculator.
Common mistakes
- Forgetting to clear a previous calculation.
- Entering a percentage as a whole number when a decimal is needed.
- Dividing by zero.
- Rounding too early in a multi-step calculation.
Practical use cases
Everyday math
Check totals, split bills, scale recipes, and estimate discounts.
School and work
Verify arithmetic, rates, quantities, and simple business calculations.
Frequently asked questions
Can I use decimals and negative numbers?
Yes. Use the decimal key and the +/- key to enter signed values.
How does the percent key work?
It divides the displayed number by 100; for example, 20 becomes 0.2.
Why does the calculator show Error?
Error appears for an undefined operation such as division by zero or a non-finite result.
Sources and review
- SI Brochure: The International System of Units — BIPM. Accessed 2026-07-14.
Reviewed 2026-07-14.