Fraction calculator
Add, subtract, multiply and divide fractions, mixed numbers and finite decimals exactly.
- 1Add input
- 2Review and run
- 3Get your result
Tool input and files are processed in this browser without being uploaded.
Before you start
Use exact fraction arithmetic for tape measurements, recipes and other values that should not be rounded before calculation. Enter two values, choose an operation and see the reduced fraction, readable mixed number and decimal.
How to use this tool
- Enter two values, such as 21 3/8 and 1 7/16.
- Choose add, subtract, multiply or divide and check the live preview.
- Calculate, then copy the mixed number, reduced fraction or decimal. The downloaded TXT contains the exact fraction.
Supported inputs and limits
Enter numbers only. This tool does not convert feet, inches, cups or other units; use the same unit for both measurements.
Accepts simple fractions, mixed numbers with a space, whole numbers and finite decimals up to 18 decimal places. Each input is limited to 120 characters.
The decimal is rounded to 12 places when it does not terminate; the fraction remains exact. Calculation stays in your browser.
Worked example
Example input
21 3/8
Example options
{"other":"1 7/16","operation":"subtract"}Example output
319/16
When something does not work
Check both values and the denominator. Use a space in mixed numbers such as 2 3/8; division by zero is undefined.
Frequently asked questions
Can I subtract two tape-measure fractions?
Yes. Enter both measurements in the same unit, for example 21 3/8 minus 1 7/16. The exact result is 19 15/16. Include any saw kerf separately; this tool does not infer cut width.
Does it accept mixed numbers and decimals?
Yes. Enter mixed numbers with a space, such as 2 3/8. Finite decimals such as 0.125 are converted to exact fractions before calculation.
Is the decimal exact?
The fraction is exact. A decimal is labeled approximate and rounded to 12 places when the expansion does not terminate within that precision.
Is my input uploaded?
No. The calculation runs in your browser; save the result you need before closing the tab.
Documentation & further reading
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