diff --git a/f3probe.c b/f3probe.c
index 969ee9f..bb8e6ff 100644
--- a/f3probe.c
+++ b/f3probe.c
@@ -348,18 +348,24 @@ static void report_cache(const char *prefix, uint64_t cache_size_block,
 		need_reset ? "yes" : "no");
 }
 
+static void report_probe_time(const char *prefix, uint64_t usec)
+{
+	char str[TIME_STR_SIZE];
+	usec_to_str(usec, str);
+	printf("%s %s\n", prefix, str);
+}
+
 static void report_ops(const char *op, uint64_t count, uint64_t time_us)
 {
-	printf("Probe %s op: count=%" PRIu64
-		", total time=%.2fs, avg op time=%.2fms\n",
-		op, count, time_us / 1e6,
-		count > 0 ? (time_us / count) / 1e3 : 0.0);
+	char str1[TIME_STR_SIZE], str2[TIME_STR_SIZE];
+	usec_to_str(time_us, str1);
+	usec_to_str(count > 0 ? time_us / count : 0, str2);
+	printf("%10s: %s / %" PRIu64 " = %s\n", op, str1, count, str2);
 }
 
 static int test_device(struct args *args)
 {
 	struct timeval t1, t2;
-	double time_s;
 	struct device *dev, *pdev, *sdev;
 	enum fake_type fake_type;
 	uint64_t real_size_byte, announced_size_byte, cache_size_block;
@@ -479,7 +485,6 @@ static int test_device(struct args *args)
 		break;
 	}
 
-	time_s = (t2.tv_sec - t1.tv_sec) + (t2.tv_usec - t1.tv_usec)/1000000.;
 	printf("\nDevice geometry:\n");
 	  report_size("\t         *Usable* size:", real_size_byte,
 		block_order);
@@ -489,12 +494,13 @@ static int test_device(struct args *args)
 	 report_cache("\tApproximate cache size:", cache_size_block,
 		need_reset, block_order);
 	 report_order("\t   Physical block size:", block_order);
-	printf("\nProbe time: %.2f seconds\n", time_s);
+	report_probe_time("\nProbe time:", diff_timeval_us(&t1, &t2));
 
 	if (args->time_ops) {
-		report_ops("read", read_count, read_time_us);
-		report_ops("write", write_count, write_time_us);
-		report_ops("reset", reset_count, reset_time_us);
+		printf(" Operation: total time / count = avg time\n");
+		report_ops("Read", read_count, read_time_us);
+		report_ops("Write", write_count, write_time_us);
+		report_ops("Reset", reset_count, reset_time_us);
 	}
 
 	free((void *)final_dev_filename);
diff --git a/libutils.c b/libutils.c
index 7485c3c..95d3d3a 100644
--- a/libutils.c
+++ b/libutils.c
@@ -59,6 +59,83 @@ const char *adjust_unit(double *ptr_bytes)
 	return units[i];
 }
 
+#define USEC_IN_A_MSEC	1000ULL
+#define USEC_IN_A_SEC	(1000*USEC_IN_A_MSEC)
+#define USEC_IN_A_MIN	(60*USEC_IN_A_SEC)
+#define USEC_IN_AN_HOUR	(60*USEC_IN_A_MIN)
+#define USEC_IN_A_DAY	(24*USEC_IN_AN_HOUR)
+
+int usec_to_str(uint64_t usec, char *str)
+{
+	int has_d, has_h, has_m, has_s;
+	lldiv_t div;
+	int c, tot = 0;
+
+	has_d = usec >= USEC_IN_A_DAY;
+	if (has_d) {
+		div = lldiv(usec, USEC_IN_A_DAY);
+		usec = div.rem;
+		c = sprintf(str + tot, "%i days", (int)div.quot);
+		assert(c > 0);
+		tot += c;
+	}
+
+	has_h = usec >= USEC_IN_AN_HOUR;
+	if (has_h) {
+		div = lldiv(usec, USEC_IN_AN_HOUR);
+		usec = div.rem;
+		c = sprintf(str + tot, "%s%i:",
+			has_d ? " " : "", (int)div.quot);
+		assert(c > 0);
+		tot += c;
+	}
+
+	has_m = has_h || usec >= USEC_IN_A_MIN;
+	if (has_m) {
+		div = lldiv(usec, USEC_IN_A_MIN);
+		usec = div.rem;
+		if (has_h)
+			c = sprintf(str + tot, "%02i", (int)div.quot);
+		else
+			c = sprintf(str + tot, "%i'", (int)div.quot);
+		assert(c > 0);
+		tot += c;
+	}
+
+	has_s = usec >= USEC_IN_A_SEC;
+	if (has_s) {
+		div = lldiv(usec, USEC_IN_A_SEC);
+		usec = div.rem;
+		if (has_h)
+			c = sprintf(str + tot, ":%02i", (int)div.quot);
+		else if (has_m)
+			c = sprintf(str + tot, "%02i\"", (int)div.quot);
+		else if (has_d)
+			c = sprintf(str + tot, "%is", (int)div.quot);
+		else
+			c = sprintf(str + tot, "%i.%02is", (int)div.quot,
+				(int)(usec / (10 * USEC_IN_A_MSEC)));
+		assert(c > 0);
+		tot += c;
+	}
+
+	if (has_d || has_h || has_m || has_s)
+		return tot;
+
+	if (usec >= USEC_IN_A_MSEC) {
+		div = lldiv(usec, USEC_IN_A_MSEC);
+		usec = div.rem;
+		c = sprintf(str + tot, "%i.%ims", (int)div.quot,
+			(int)(usec / 100));
+	} else {
+		c = sprintf(str + tot, "%ius", (int)usec);
+	}
+	assert(c > 0);
+	tot += c;
+
+	return tot;
+}
+
 void *align_mem(void *p, int order)
 {
 	uintptr_t ip = (uintptr_t)p;
diff --git a/libutils.h b/libutils.h
index 2c76219..18dd137 100644
--- a/libutils.h
+++ b/libutils.h
@@ -16,6 +16,10 @@ int ceiling_log2(uint64_t x);
 
 const char *adjust_unit(double *ptr_bytes);
 
+#define TIME_STR_SIZE	128
+
+int usec_to_str(uint64_t usec, char *str);
+
 /*
  * The functions align_head() and align_mem() are used to align pointers.
  *