diff --git a/cols.1 b/cols.1
index c027118..179ff0a 100644
--- a/cols.1
+++ b/cols.1
@@ -1,4 +1,4 @@
-.Dd February 1, 2015
+.Dd February 19, 2015
 .Dt COLS 1
 .Os sbase
 .Sh NAME
@@ -20,16 +20,24 @@ character columns. If no
 is given,
 .Nm
 reads from stdin.
+.Pp
+By default
+.Nm cols
+tries to figure out the width of the output
+device. If that fails, it defaults to 65 chars.
 .Sh OPTIONS
 .Bl -tag -width Ds
 .It Fl c Ar chars
 Set the maximum number of character columns to use
 (unless the input contains lines longer than
 .Ar num
-characters). By default
-.Nm cols
-tries to figure out the width of the output
-device. If that fails, it defaults to 65 chars.
+characters).
+.El
+.Sh ENVIRONMENT
+.Bl -tag -width COLUMNS
+.It COLUMNS
+If this variable is set, the value is used as the
+width of the output device.
 .El
 .Sh HISTORY
 .Nm
diff --git a/cols.c b/cols.c
index 572dbe0..a48c576 100644
--- a/cols.c
+++ b/cols.c
@@ -31,6 +31,7 @@ main(int argc, char *argv[])
 	size_t i, l, col, len, bytes, maxlen = 0;
 	struct winsize w;
 	FILE *fp;
+	char *p;
 
 	ARGBEGIN {
 	case 'c':
@@ -42,8 +43,9 @@ main(int argc, char *argv[])
 	} ARGEND;
 
 	if (cflag == 0) {
-		ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
-		if (w.ws_col != 0)
+		if ((p = getenv("COLUMNS")))
+			chars = estrtonum(p, 1, MIN(LLONG_MAX, SIZE_MAX));
+		else if (!ioctl(STDOUT_FILENO, TIOCGWINSZ, &w) && w.ws_col > 0)
 			chars = w.ws_col;
 	}