diff --git a/Makefile b/Makefile
index 0826caa5..bcaad190 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,8 @@ FTL_DEPS = *.h database/*.h api/*.h version.h
 FTL_DB_OBJ = database/common.o database/query-table.o database/network-table.o database/gravity-db.o database/database-thread.o \
              database/sqlite3-ext.o database/message-table.o
 FTL_API_OBJ = api/http-common.o api/routes.o api/ftl.o api/stats.o api/dns.o api/version.o api/auth.o api/settings.o api/stats_database.o
-FTL_OBJ = $(FTL_DB_OBJ) $(FTL_API_OBJ) main.o memory.o log.o daemon.o datastructure.o signals.o files.o setupVars.o args.o gc.o config.o dnsmasq_interface.o resolve.o regex.o shmem.o capabilities.o overTime.o timers.o vector.o
+FTL_OBJ = $(FTL_DB_OBJ) $(FTL_API_OBJ) main.o memory.o log.o daemon.o datastructure.o signals.o files.o setupVars.o args.o gc.o config.o \
+          dnsmasq_interface.o resolve.o regex.o shmem.o capabilities.o overTime.o timers.o vector.o math.o
 
 DNSMASQ_DEPS = config.h dhcp-protocol.h dns-protocol.h radv-protocol.h dhcp6-protocol.h dnsmasq.h ip6addr.h metrics.h ../dnsmasq_interface.h
 DNSMASQ_OBJ = arp.o dbus.o domain.o lease.o outpacket.o rrfilter.o auth.o dhcp6.o edns0.o log.o poll.o slaac.o blockdata.o dhcp.o forward.o \
diff --git a/src/api/stats.c b/src/api/stats.c
index 717a9a99..017b98a8 100644
--- a/src/api/stats.c
+++ b/src/api/stats.c
@@ -26,6 +26,8 @@
 #include "overTime.h"
 // enum REGEX
 #include "regex_r.h"
+// my_sqrt()
+#include "../math.h"
 
 /* qsort comparision function (count field), sort ASC
 static int __attribute__((pure)) cmpasc(const void *a, const void *b)
@@ -471,6 +473,7 @@ int api_stats_upstreams(struct mg_connection *conn)
 	{
 		int count = 0;
 		const char* ip, *name;
+		double responsetime = 0.0, uncertainty = 0.0;
 
 		if(i == -2)
 		{
@@ -503,6 +506,20 @@ int api_stats_upstreams(struct mg_connection *conn)
 
 			// Get percentage
 			count = forward->count;
+
+			// Compute average response time and uncertainty (unit: seconds)
+			if(forward->responses > 0)
+			{
+				// Wehave to multiply runcertainty by 1e-4 to get seconds
+				responsetime = 1e-4 * forward->rtime / forward->responses;
+			}
+			if(forward->responses > 1)
+			{
+				// The actual value will be somewhere in a neighborhood around the mean value.
+				// This neighborhood of values is the uncertainty in the mean.
+				// Wehave to multiply runcertainty by (1e-4)^2 to get seconds
+				uncertainty = my_sqrt(1e-8 * forward->rtuncertainty / forward->responses / (forward->responses-1));
+			}
 		}
 
 		// Send data:
@@ -514,6 +531,8 @@ int api_stats_upstreams(struct mg_connection *conn)
 			JSON_OBJ_REF_STR(upstream, "name", name);
 			JSON_OBJ_REF_STR(upstream, "ip", ip);
 			JSON_OBJ_ADD_NUMBER(upstream, "count", count);
+			JSON_OBJ_ADD_NUMBER(upstream, "responsetime", responsetime);
+			JSON_OBJ_ADD_NUMBER(upstream, "uncertainty", uncertainty);
 			JSON_ARRAY_ADD_ITEM(upstreams, upstream);
 		}
 	}
diff --git a/src/datastructure.c b/src/datastructure.c
index eb3adf08..c3f8afa5 100644
--- a/src/datastructure.c
+++ b/src/datastructure.c
@@ -76,6 +76,10 @@ int findUpstreamID(const char * upstreamString, const bool count)
 	// to be done separately to be non-blocking
 	upstream->new = true;
 	upstream->namepos = 0; // 0 -> string with length zero
+	// Initialize response time values
+	upstream->rtime = 0u;
+	upstream->rtuncertainty = 0u;
+	upstream->responses = 0u;
 	// Increase counter by one
 	counters->upstreams++;
 
diff --git a/src/datastructure.h b/src/datastructure.h
index b573f4b5..4deebb07 100644
--- a/src/datastructure.h
+++ b/src/datastructure.h
@@ -47,6 +47,9 @@ typedef struct {
 typedef struct {
 	unsigned char magic;
 	bool new;
+	unsigned long rtime;
+	unsigned long rtuncertainty;
+	unsigned int responses;
 	int count;
 	int failed;
 	size_t ippos;
diff --git a/src/dnsmasq_interface.c b/src/dnsmasq_interface.c
index 165b34e5..d829562b 100644
--- a/src/dnsmasq_interface.c
+++ b/src/dnsmasq_interface.c
@@ -961,6 +961,14 @@ void _FTL_reply(const unsigned short flags, const char *name, const union all_ad
 	}
 	else if((flags & F_FORWARD) && isExactMatch)
 	{
+		// Save query response time
+		upstreamsData *upstream = getUpstream(query->upstreamID, true);
+		upstream->responses++;
+		unsigned long rtime = converttimeval(response) - query->response;
+		upstream->rtime += rtime;
+		unsigned long mean = upstream->rtime / upstream->responses;
+		upstream->rtuncertainty += (mean - rtime)*(mean - rtime);
+
 		// Only proceed if query is not already known
 		// to have been blocked by Quad9
 		if(query->reply != QUERY_EXTERNAL_BLOCKED_IP &&
diff --git a/src/math.c b/src/math.c
new file mode 100644
index 00000000..d0a66be6
--- /dev/null
+++ b/src/math.c
@@ -0,0 +1,52 @@
+/* Pi-hole: A black hole for Internet advertisements
+*  (c) 2019 Pi-hole, LLC (https://pi-hole.net)
+*  Network-wide ad blocking via your own hardware.
+*
+*  FTL Engine
+*  Math Implementation
+*
+*  This file is copyright under the latest version of the EUPL.
+*  Please see LICENSE file for your rights under this license. */
+
+#include "math.h"
+
+// Recursive function that returns square root
+// of a number with precision upto 5 decimal places
+double Square(double n, double i, double j)
+{
+	double mid = (i + j) / 2;
+	double mul = mid * mid;
+
+	if ((mul - n)*(mul - n) < (SQRT_PRECISION * SQRT_PRECISION))
+	{
+		return mid;
+	}
+	else if (mul < n)
+	{
+		return Square(n, mid, j);
+	}
+	else
+	{
+		return Square(n, i, mid);
+	}
+}
+
+	// Function to find the square root of n 
+double my_sqrt(double n) 
+{
+	// While the square root is not found 
+	for(double i = 1.0; true; i++)
+	{
+		if ((i - n)*(i - n) < (SQRT_PRECISION * SQRT_PRECISION))
+		{
+			// If n is a perfect square 
+			return i;
+		}
+		else if (i * i > n)
+		{
+			// Square root will lie in the interval i-1 and i
+			return Square(n, i - 1, i);
+		}
+		i++;
+	}
+} 
\ No newline at end of file
diff --git a/src/math.h b/src/math.h
new file mode 100644
index 00000000..ec59b48e
--- /dev/null
+++ b/src/math.h
@@ -0,0 +1,25 @@
+/* Pi-hole: A black hole for Internet advertisements
+*  (c) 2019 Pi-hole, LLC (https://pi-hole.net)
+*  Network-wide ad blocking via your own hardware.
+*
+*  FTL Engine
+*  Math Prototypes
+*
+*  This file is copyright under the latest version of the EUPL.
+*  Please see LICENSE file for your rights under this license. */
+
+#ifndef MATH_H
+#define MATH_H
+
+#include <stdlib.h>
+#include <stdbool.h>
+
+#define SQRT_PRECISION 1e-5
+
+// Recursive function that returns square root
+double Square(double n, double i, double j);
+  
+// Function to find the square root of n 
+double my_sqrt(double n); 
+
+#endif //MATH_H
\ No newline at end of file