diff --git a/mc.1 b/mc.1
index f1c9a0f..b7ce4e3 100644
--- a/mc.1
+++ b/mc.1
@@ -19,9 +19,9 @@ If no file is given, mc reads from stdin.
 specifies the maximum number of character columns to use
 (unless the input contains lines longer than
 .I chars
-characters).
-.I chars
-defaults to 65.
+characters).  By default mc tries to figure out the width
+of the output device, if that fails it defaults to 65
+chars.
 .SH BUGS
 This implementation of
 .B mc
@@ -32,5 +32,4 @@ or TAB characters correctly.
 .B mc
 currently mangles files which contain embedded NULs.
 .B mc
-does not attempt to determine the width of its output device,
-nor does it allow the user to set a default width in its environment.
+does not allow the user to set a default width in its environment.
diff --git a/mc.c b/mc.c
index 381885d..411ce58 100644
--- a/mc.c
+++ b/mc.c
@@ -5,10 +5,12 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <sys/ioctl.h>
 #include "text.h"
 #include "util.h"
 
 static long chars = 65;
+static int cflag;
 static struct linebuf b = EMPTY_LINEBUF;
 
 static long n_columns;
@@ -26,10 +28,12 @@ main(int argc, char *argv[])
 	long i, l, col;
 	size_t maxlen = 0;
 	char *space;
+	struct winsize w;
 	FILE *fp;
 
 	ARGBEGIN {
 	case 'c':
+		cflag = 1;
 		chars = estrtol(EARGF(usage()), 0);
 		if(chars < 3)
 			eprintf("%d: too few character columns");
@@ -38,6 +42,12 @@ main(int argc, char *argv[])
 		usage();
 	} ARGEND;
 
+	if (cflag == 0) {
+		ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
+		if (w.ws_col != 0)
+			chars = w.ws_col;
+	}
+
 	/* XXX librarify this chunk, too?  only useful in sponges though */
 	if(argc == 0) {
 		getlines(stdin, &b);
@@ -84,4 +94,3 @@ main(int argc, char *argv[])
 
 	return EXIT_SUCCESS;
 }
-