What is the difference between single and double precision?

Single precision (32-bit) uses 1 sign bit, 8 exponent bits and 23 mantissa bits. Double precision (64-bit) uses 1 sign bit, 11 exponent bits and 52 mantissa bits, giving far more range and accuracy.

Why does my number not convert exactly?

Many decimal fractions like 0.1 cannot be represented exactly in binary floating point. The converter shows the exact bit pattern that is actually stored, which is the nearest representable value.

Is anything uploaded?

No — the conversion uses your browser's own typed-array support and nothing is sent to a server.

IEEE 754 Floating-Point Converter

IEEE 754 floating-point converter

Convert any decimal number into its IEEE 754 representation in 32-bit single or 64-bit double precision. The tool shows the hexadecimal value, the full binary pattern, and breaks the number into its three fields: the sign bit, the biased exponent, and the mantissa.

IEEE 754 is the floating-point standard used by virtually every programming language and CPU. Because many decimals cannot be stored exactly in binary, the bits you see are the nearest representable value — computed locally in your browser.