diff --git a/lib/libc/gen/humanize_number.3 b/lib/libc/gen/humanize_number.3
index e2fb1d1ed915..60e5aa984f5f 100644
--- a/lib/libc/gen/humanize_number.3
+++ b/lib/libc/gen/humanize_number.3
@@ -1,6 +1,6 @@
-.\"	$NetBSD: humanize_number.3,v 1.6 2007/12/14 16:31:20 xtraeme Exp $
+.\"	$NetBSD: humanize_number.3,v 1.7 2008/02/09 09:09:04 jmmv Exp $
 .\"
-.\" Copyright (c) 1999, 2002 The NetBSD Foundation, Inc.
+.\" Copyright (c) 1999, 2002, 2008 The NetBSD Foundation, Inc.
 .\" All rights reserved.
 .\"
 .\" This code is derived from software contributed to The NetBSD Foundation
@@ -34,15 +34,18 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd December 14, 2007
+.Dd February 9, 2008
 .Dt HUMANIZE_NUMBER 3
 .Os
 .Sh NAME
+.Nm dehumanize_number ,
 .Nm humanize_number
-.Nd format a number into a human readable form
+.Nd format a number into a human readable form and viceversa
 .Sh SYNOPSIS
 .In stdlib.h
 .Ft int
+.Fn dehumanize_number "const char *str" "int64_t *result"
+.Ft int
 .Fn humanize_number "char *buf" "size_t len" "int64_t number" "const char *suffix" "int scale" "int flags"
 .Sh DESCRIPTION
 The
@@ -120,6 +123,15 @@ Divide
 .Fa number
 with 1000 instead of 1024.
 .El
+.Pp
+The
+.Fn dehumanize_number
+function parses the string representing an integral value given in
+.Fa str
+and stores the numerical value in the integer pointed to by
+.Fa result .
+The provided string may hold one of the suffixes, which will be interpreted
+and used to scale up its accompanying numerical value.
 .Sh RETURN VALUES
 .Fn humanize_number
 returns the number of characters stored in
@@ -128,9 +140,34 @@ returns the number of characters stored in
 If
 .Dv HN_GETSCALE
 is specified, the prefix index number will be returned instead.
+.Pp
+.Fn dehumanize_number
+returns 0 if the string was parsed correctly.
+A \-1 is returned to indicate failure and an error code is stored in
+.Va errno .
+.Sh ERRORS
+.Fn dehumanize_number
+will fail and no number will be stored in
+.Fa result
+if:
+.Bl -tag -width Er
+.It Bq Er EINVAL
+The string in
+.Fa str
+was empty or carried an unknown suffix.
+.It Bq Er ERANGE
+The string in
+.Fa str
+represented a number that does not fit in
+.Fa result .
+.El
 .Sh SEE ALSO
 .Xr humanize_number 9
 .Sh HISTORY
 .Fn humanize_number
 first appeared in
 .Nx 2.0 .
+.Pp
+.Fn dehumanize_number
+first appeared in
+.Nx 5.0 .