XSLT Cookbook

Rounding Numbers to a Specified Precision

Problem

You want to round to a specific number of decimal places; however, XSLT’s round, ceiling, and floor functions always map numbers to integer values.

Solution

Multiply, round, and divide using a power of ten that determines how many decimal digits are required. Assuming $pi = 3.1415926535897932:

<xsl:value-of select="round($pi * 10000) div 10000"/>

results in 3.1416. Similarily:

<xsl:value-of select="ceiling($pi * 10000) div 10000"/>

results in 3.1416, and:

<xsl:value-of select="floor($pi * 10000) div 10000"/>

results in 3.1415.

Rounding to a specific number of decimal places is also achieved using format-number( ):

<xsl:value-of select="format-number($pi,'#.####')"/>

This results in 3.1416. This will work even if more than one significant digit is in the whole part because format-number never uses a format specification as an indication to remove significant digits from the whole part:

<xsl:value-of select="format-number($pi * 100,'#.####')"/>

This results in 314.1593.

You can use format-number to get the effect of truncating rather than rounding by using one more formatting digit than required and then chopping off the last character:

<xsl:variable name="pi-to-5-sig" select="format-number($pi,'#.#####')"/>
<xsl:value-of select="substring($pi-to-5-sig,1,string-length($pi-to-5-sig) -1)"/>

This results in 3.1415.

Discussion

This multiply, round, and divide technique works well as long as the numbers involved remain within the representational ...