Basic Calculator Online
Free online basic calculator: add, subtract, multiply, divide, percent, square root, brackets and memory. Runs in your browser, with a history of results. Calculate. Check. Understand.
History
Results you confirm with = appear here. Select one to use its expression again. History stays in this page and is not stored.
How to use it
Type an expression on the keyboard or use the keypad, and the result appears as you type. Press Enter or = to confirm a result and add it to the history. Escape or AC clears the expression.
- Use * and / or the × and ÷ keys. Write a decimal point, not a comma.
- Brackets can be nested, as in
((2+3)*4-5)/3. - After a confirmed result, typing + − × ÷ continues from the answer, and typing a digit starts a new calculation.
The keys
| Key | What it does | Example | Result |
|---|---|---|---|
| + − × ÷ | Add, subtract, multiply and divide. You can also type * and / | 12.5*8 | 100 |
| ( ) | Brackets: what is inside is worked out first | (2+3)*4 | 20 |
| % | Divides the value before it by 100 | 200*15% | 30 |
| √ | Square root | sqrt(144) | 12 |
| x² | Square of the whole expression | (7)^2 | 49 |
| 1/x | Reciprocal of the whole expression | 1/(8) | 0.125 |
| ± | Changes the sign of the whole expression | -(5) | -5 |
| Ans | The previous confirmed answer | ans*2 after 21 | 42 |
Every result in this table is calculated by the same engine as the calculator above.
Order of operations
The calculator follows the usual rules of mathematics, not the order in which you press the keys:
| Expression | Rule | Result |
|---|---|---|
| 2+3*4 | Multiply before adding | 14 |
| (2+3)*4 | Brackets first | 20 |
| 10-4-3 | Subtract left to right | 3 |
| 100/4/5 | Divide left to right | 5 |
| -2^2 | The power is worked out before the minus | -4 |
Working with percent
The % key divides by 100, so a percentage of a number is the number times the percentage: 15% of 200 is 200*15% = 30. To add a percentage, multiply by one plus the percentage: 200 plus 10 percent is 200*(1+10%) = 220, and 200 minus 10 percent is 200*(1-10%) = 180.
Accuracy checks
These results are produced by the same engine and are checked by the site’s tests:
| Calculation | Result |
|---|---|
| 0.1 + 0.2 | 0.3 |
| 12.5 × 8 | 100 |
| 1 ÷ 3 | 0.3333333333 |
| √2 | 1.414213562 |
| 15% of 200 | 30 |
| 1 ÷ 0 | Error: division by zero |
Numbers are double precision (about 15 to 17 significant digits) and the display shows 10. For engineering work with more digits, choose the number of digits in the Scientific Calculator.
Frequently asked questions
How does this calculator read what I type?
It uses its own expression parser, the same one as the Scientific Calculator. It does not use eval or run your text as code, and nothing you type leaves your browser. Multiplication and division are worked out before addition and subtraction, and brackets are worked out first.
Does it work like a pocket calculator that does one operation at a time?
No. You type the whole expression and see the result as you go, so 2+3*4 is 14, as in mathematics, and not 20. To work step by step, press = after each step and continue from the answer: typing an operator after = starts from the previous answer.
What does the % key do?
It divides the value before it by 100, so 200*15% is 30. It does not add a percentage to a total as some pocket calculators do: 200+10% is 200.1. For 200 plus 10 percent write 200*(1+10%), which is 220. The Percentage Calculator on this site handles increase, decrease and percentage change.
Why does 0.1 + 0.2 show 0.3?
Calculations use double-precision numbers, which hold about 15 to 17 significant digits. The display rounds to 10 significant digits, so the tiny binary rounding error in 0.1 + 0.2 does not show.
What happens when I divide by zero?
The calculator shows an error message and no result. A very large or very small result is shown in scientific form, such as 1.5×10¹⁵.
How do I use memory?
M+ adds the current result (or the expression you typed) to memory, M− subtracts it, MR puts the memory value into the expression and MC clears it. Memory is held in the page and disappears when you close it.
Does it keep my calculations?
No. The history and memory are held in the page and disappear when you close it. Nothing is stored or sent.
When should I use the Scientific Calculator instead?
Use it for trigonometry, logarithms, powers and roots of any order, factorials, complex numbers, polar form and SI prefixes for electrical work.