Decimal Calculator
Perform arithmetic operations on decimal numbers with full precision. Add, subtract, multiply, or divide decimals without floating-point display errors. Results are shown with appropriate precision for clean, accurate output.
How to Use the Decimal Calculator
- Enter the first decimal number in the left field.
- Select the arithmetic operation (add, subtract, multiply, or divide).
- Enter the second decimal number in the right field.
- Click Calculate to see the result with full precision.
- The result avoids common floating-point display errors (e.g., 0.1 + 0.2 shows 0.3, not 0.30000000000000004).
Formula
Standard arithmetic operations on decimal numbers:
Addition: a + b
Subtraction: a - b
Multiplication: a × b
Division: a ÷ b (b ≠ 0)
Precision rules:
Addition/Subtraction: result has same decimal places as input with most decimals
Multiplication: result can have up to (decimals of a + decimals of b) places
Division: result shown up to 10 decimal places (trailing zeros removed)Example
Perform 3.14 + 2.71:
3.14 + 2.71 = 5.85
More examples:
0.1 + 0.2 = 0.3 (not 0.30000000000000004)
3.14 × 2.71 = 8.5094
10.5 ÷ 3 = 3.5
7.89 - 4.56 = 3.33Decimal Operations Reference Table
| Operation | Expression | Result |
|---|---|---|
| Addition | 0.1 + 0.2 | 0.3 |
| Addition | 1.25 + 3.75 | 5 |
| Subtraction | 5.5 - 2.3 | 3.2 |
| Subtraction | 10 - 0.01 | 9.99 |
| Multiplication | 2.5 × 4.2 | 10.5 |
| Multiplication | 0.3 × 0.3 | 0.09 |
| Division | 10 ÷ 3 | 3.3333333333 |
| Division | 7.5 ÷ 2.5 | 3 |
Frequently Asked Questions
What is a decimal number?
A decimal number uses a decimal point to represent fractions of whole numbers. For example, 3.14 means 3 whole units plus 14 hundredths. The digits after the decimal point represent tenths, hundredths, thousandths, etc.
Why does 0.1 + 0.2 not equal 0.3 in computers?
Computers use binary floating-point representation, which cannot exactly represent some decimal fractions (like 0.1). This causes tiny rounding errors. Our calculator handles this by applying appropriate precision to display clean results.
How do I add decimals by hand?
Line up the decimal points vertically, pad with zeros if needed so both numbers have the same decimal places, then add column by column from right to left, carrying over as needed. Place the decimal point in the same position in the answer.
What is rounding and when should I round?
Rounding reduces the number of decimal places. Round when you need a practical answer (e.g., money to 2 decimal places). The standard rule: if the next digit is 5 or more, round up; otherwise, round down.
How many decimal places should my answer have?
For addition and subtraction, use the same number of decimal places as the least precise input. For multiplication, the result can have up to the sum of decimal places of both inputs. For division, use as many places as needed for your application.