diff --git a/man3/nextup.3 b/man3/nextup.3
new file mode 100644
index 000000000..2555cebc1
--- /dev/null
+++ b/man3/nextup.3
@@ -0,0 +1,93 @@
+.\" Copyright (C) 2016, Michael Kerrisk <mtk.manpages@gmail.com>
+.\"
+.\" %%%LICENSE_START(VERBATIM)
+.\" Permission is granted to make and distribute verbatim copies of this
+.\" manual provided the copyright notice and this permission notice are
+.\" preserved on all copies.
+.\"
+.\" Permission is granted to copy and distribute modified versions of this
+.\" manual under the conditions for verbatim copying, provided that the
+.\" entire resulting derived work is distributed under the terms of a
+.\" permission notice identical to this one.
+.\"
+.\" Since the Linux kernel and libraries are constantly changing, this
+.\" manual page may be incorrect or out-of-date.  The author(s) assume no
+.\" responsibility for errors or omissions, or for damages resulting from
+.\" the use of the information contained herein.  The author(s) may not
+.\" have taken the same level of care in the production of this manual,
+.\" which is licensed free of charge, as they might when working
+.\" professionally.
+.\"
+.\" Formatted or processed versions of this manual, if unaccompanied by
+.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
+.\"
+.TH NEXTUP 3 2016-07-15 "GNU" "Linux Programmer's Manual"
+.SH NAME
+nextup, nextupf, nextupl, nextdown, nextdownf, nextdownl \-
+return next floating-point number toward positive/negative infinity
+.SH SYNOPSIS
+.nf
+.BR "#define _GNU_SOURCE" "     /* See feature_test_macros(7) */"
+.B #include <math.h>
+
+.BI "double nextup(double " x );
+.BI "float nextupf(float " x );
+.BI "long double nextupl(long double " x );
+
+.BI "double nextdown(double " x );
+.BI "float nextdownf(float " x );
+.BI "long double nextdownl(long double " x );
+
+Link with \fI\-lm\fP.
+.SH DESCRIPTION
+The
+.BR nextup (),
+.BR nextupf (),
+and
+.BR nextupl ()
+functions return the next representable floating-point number greater than
+.IR x .
+
+If
+.I x
+is the smallest representable negative number in the corresponding type,
+these functions return \-0.
+If
+.I x
+is 0, the returned value is the smallest representable positive number
+of the corresponding type.
+
+If
+.I x
+is positive infinity, the returned value is positive infinity.
+If
+.I x
+is negative infinity,
+the returned value is the largest representable finite negative number
+of the corresponding type.
+
+If
+.I x
+is Nan,
+the returned value is NaN.
+
+The value returned by
+.IR nextdown(x)
+is
+.IR \-nextup(\-x) ,
+and similarly for the other types.
+.SH RETURN VALUE
+See DESCRIPTION.
+.\" .SH ERRORS
+.\" .SH ATTRIBUTES
+.SH VERSIONS
+These functions first appeared in glibc in version 2.24.
+.SH CONFORMING TO
+These functions are described in
+.IR "IEEE Std 754-2008 - Standard for Floating-Point Arithmetic"
+and
+.IR "ISO/IEC TS 18661".
+.SH SEE ALSO
+.BR nearbyint (3),
+.BR nextafter (3)