Concepts · 3 min read

Why 0.1 + 0.2 Is Not Exactly 0.3 in Computers

Published October 3, 2026Written and reviewed by Mateuss M.

Binary cannot write 0.1 exactly

Just as 1/3 becomes 0.333… in decimal, 1/10 becomes an endless repeating pattern in binary. A computer stores only a fixed number of binary digits, so it keeps the nearest value it can — slightly above or below the true 0.1.

Add two such approximations and the tiny errors can surface in the last digits. That is the famous 0.30000000000000004.

What this calculator does about it

CalcSolver Pro evaluates with standard double-precision numbers, then cleans the result to 12 significant digits. That hides the 17th-digit noise while keeping far more precision than any classroom problem needs.

When exactness matters

Fraction tools avoid the problem entirely: they use whole-number numerators and denominators and only produce a decimal at the very end. Money software typically stores whole cents for the same reason.

Frequently asked questions

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