Decimal Calculator
Decimal Calculator works out Result and Unrounded result from Expression, Variables (optional) and Number display. The default figures on this page give result of 0.3; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
3 steps
- Evaluate 0.1 + 0.2 in exact fraction arithmetic.
- 1/10 + 1/5 = 3/10
- In binary floating point the same expression gives 0.30000000000000004; the exact value is 3/10 = 0.3.
Step-by-step workingtable
Its 12 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
What the Decimal Calculator calculates
Adds, subtracts, multiplies, divides and exponentiates numbers, either as a free-form expression evaluated with correct operator precedence, as two named operands, as a list folded left to right, or as a sum written out in words — in binary floating point or in exact fraction arithmetic.
How to use this Decimal Calculator
Enter Expression, Variables (optional), Number display and Working shown. Result updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Result, Unrounded result and Expression evaluated.
The method follows ISO 80000-2, Quantities and units — Part 2: Mathematics (operator symbols and precedence), NIST Digital Library of Mathematical Functions, §1.1 Notation, IEEE 754-2019, Standard for Floating-Point Arithmetic and Unicode CLDR number formatting patterns (es-ES decimal comma, en-IN lakh/crore grouping).
What you can compare
Change one input at a time to see how it affects Result, Unrounded result and Expression evaluated. The inputs you can vary are Expression, Variables (optional), Number display and Working shown.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I get my calculator to show decimals?
Adds, subtracts, multiplies, divides and exponentiates numbers, either as a free-form expression evaluated with correct operator precedence, as two named operands, as a list folded left to right. Open “How this is worked out” beside the result to see each step for your own figures.
How to turn calculator into decimal?
It needs Expression, Variables (optional), Number display and Working shown. Nothing else is required, and the figures stay in your browser.
How do I calculate a decimal number?
The result gives Result, Unrounded result, Expression evaluated, Result with separators, Result as a fraction and Whole-number quotient, each labelled with its unit so the figure can be read on its own.
Can you provide me with a decimal multiplying calculator?
Adds, subtracts, multiplies, divides and exponentiates numbers, either as a free-form expression evaluated with correct operator precedence, as two named operands, as a list folded left to right. Put your own figures in above and the working updates beside the result. For scale, the default figures on this page give 0.3.
Can you provide a decimal hours calculator?
The page opens with worked default figures: result of 0.3. Replace them with your own and every figure updates as you type.
What information do I need for the Decimal Calculator?
You need Expression, Variables (optional), Number display and Working shown. The page opens with default figures that give result of 0.3, so you can see the scale before entering your own.