This page allows you to convert between the decimal representation of numbers (like "1.02")
and the binary format used by all modern CPUs (IEEE 754 floating point).
The conversion is limited to single precision numbers (32 Bit). The purpose of this webpage is to help you understand floating point numbers.
You can either convert a number by choosing its binary representation in the button-bar, the other fields will be updated immediately. Or you can enter a binary number, a hexnumber or the decimal representation into the corresponding textfield and press return to update
the other fields. To make it easier to spot eventual rounding errors, the selected float number is displayed after conversion to double precision.
You can enter the words "Infinity", "-Infinity" or "NaN" to get the corresponding special values for IEEE-754. Please note there are two kinds of zero: +0 and -0.
The value of a IEEE-754 number is computed as:
sign * 2exponent * mantissa
The sign is stored in bit 32. The exponent can be computed from bits 24-31 by subtracting 127. The mantissa (also known as significand or fraction) is stored in bits 1-23.
An invisible leading bit (i.e. it is not actually stored) with value 1.0 is placed in front, then bit 23 has a value of 1/2, bit 22 has value 1/4 etc. As a result, the mantissa
has a value between 1.0 and 2. If the exponent reaches -127 (binary 00000000), the leading 1 is no longer used to enable gradual underflow.
Not every decimal number can be expressed exactly as a floating point number. This can be seen when entering "0.1" and examining its binary representation which is either slightly smaller or larger, depending on the last bit.
The hex representation is just the integer value of the bitstring printed as hex. Don't confuse this with true hexadecimal floating point values in the style of 0xab.12ef.
FAQ (Frequently Asked Questions):
Can I use the converter without internet connection?
The Java-based version can be used without internet connection. The necessary files can be downloaded as a ZIP file here: float_applet_offline.zip. Extract the contents to your harddisk and open the file IEEE754.html with a webbrowser (which must have Java-plugin to work). But please don't put the converter online somewhere else, link here instead.
Can you send me the source code? I need to convert format x to format y.
This source code for this converter doesn't contain any low level conversion routines. The conversion between a floating point number (i.e. a 32 bit area in memory) and the bit representation isn't actually a conversion, but just a reinterpretation of the same data in memory. This can be easily done with typecasts in C/C++ or with some bitfiddling via java.lang.Float.floatToIntBits in Java. The conversion between a string containing the textual form of a floating point number (e.g. "3.14159", a string of 7 characters) and a 32 bit floating point number is also performed by library routines. If you need to write such a routine yourself, you should have a look at the sourecode of a standard C library (e.g. GNU libc, uclibc or the FreeBSD C library - please have a look at the licenses before copying the code) - be aware, these conversions can be complicated.
I've converted a number to floating point by hand/some other method, and I get a different result. Your converter is wrong!
Possibly, but unlikely. The conversion routines are pretty accurate (see above). Until now, checking the results always proved the other conversion less accurate. In particular toggling the last bit can lead to the same result after rounding to a fixed number of decimal places. Please check the double precision result (bottom line in the converter) and compare the difference to the expected decimal result while toggling the last bit.