How this calculator works
Reduce the fraction and inspect its denominator. If the remaining prime factors are only 2 and 5, multiplying by a suitable power of ten produces an exact terminating decimal. Other denominators give repeating expansions. Those are rounded half away from zero to ten places and marked as approximations with three dots.
Formula
Decimal = n/d. A reduced denominator of 2^a × 5^b terminates within max(a, b) decimal places.
Worked example
3/8 = 0.375 exactly because 8 = 2^3. The expansion of 2/3 repeats, so its displayed approximation is 0.6666666667...
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Frequently asked questions
Do the three dots identify the repeating block?
No. They indicate that the decimal continues. The displayed digits are a rounded approximation, rather than a notation marking the repeating cycle.
Is 0/5 valid?
Yes. A zero numerator gives zero for every non-zero denominator. A zero denominator is always rejected.
Will one third ever print as an exact decimal?
No. A reduced denominator with a prime factor other than 2 or 5 repeats forever, so the page shows a rounded ten-place value marked with three dots.