diff --git a/presto-main/src/main/java/com/facebook/presto/execution/BasicStageExecutionStats.java b/presto-main/src/main/java/com/facebook/presto/execution/BasicStageExecutionStats.java
index 063ff8afb942f..20657fd8cdd89 100644
--- a/presto-main/src/main/java/com/facebook/presto/execution/BasicStageExecutionStats.java
+++ b/presto-main/src/main/java/com/facebook/presto/execution/BasicStageExecutionStats.java
@@ -42,7 +42,7 @@ public class BasicStageExecutionStats
             new DataSize(0, BYTE),
             0,
 
-            0,
+            0.0,
             new DataSize(0, BYTE),
             new DataSize(0, BYTE),
 
@@ -63,7 +63,7 @@ public class BasicStageExecutionStats
     private final int completedDrivers;
     private final DataSize rawInputDataSize;
     private final long rawInputPositions;
-    private final long cumulativeUserMemory;
+    private final double cumulativeUserMemory;
     private final DataSize userMemoryReservation;
     private final DataSize totalMemoryReservation;
     private final Duration totalCpuTime;
@@ -84,7 +84,7 @@ public BasicStageExecutionStats(
             DataSize rawInputDataSize,
             long rawInputPositions,
 
-            long cumulativeUserMemory,
+            double cumulativeUserMemory,
             DataSize userMemoryReservation,
             DataSize totalMemoryReservation,
 
@@ -151,7 +151,7 @@ public long getRawInputPositions()
         return rawInputPositions;
     }
 
-    public long getCumulativeUserMemory()
+    public double getCumulativeUserMemory()
     {
         return cumulativeUserMemory;
     }
@@ -203,7 +203,7 @@ public static BasicStageExecutionStats aggregateBasicStageStats(Iterable<BasicSt
         int runningDrivers = 0;
         int completedDrivers = 0;
 
-        long cumulativeUserMemory = 0;
+        double cumulativeUserMemory = 0;
         long userMemoryReservation = 0;
         long totalMemoryReservation = 0;
 
diff --git a/presto-main/src/main/java/com/facebook/presto/execution/QueryStats.java b/presto-main/src/main/java/com/facebook/presto/execution/QueryStats.java
index 95916dfa10c96..e2774c74c0ec6 100644
--- a/presto-main/src/main/java/com/facebook/presto/execution/QueryStats.java
+++ b/presto-main/src/main/java/com/facebook/presto/execution/QueryStats.java
@@ -269,7 +269,7 @@ public static QueryStats create(
         int blockedDrivers = 0;
         int completedDrivers = 0;
 
-        long cumulativeUserMemory = 0;
+        double cumulativeUserMemory = 0;
         long userMemoryReservation = 0;
         long totalMemoryReservation = 0;
 
diff --git a/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionInfo.java b/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionInfo.java
index e6bca564844e1..fae5d497d8b60 100644
--- a/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionInfo.java
+++ b/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionInfo.java
@@ -71,7 +71,7 @@ public static StageExecutionInfo create(
         int blockedDrivers = 0;
         int completedDrivers = 0;
 
-        long cumulativeUserMemory = 0;
+        double cumulativeUserMemory = 0;
         long userMemoryReservation = 0;
         long totalMemoryReservation = 0;
 
diff --git a/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionStateMachine.java b/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionStateMachine.java
index d756fd436fabc..43ad6ccc393ea 100644
--- a/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionStateMachine.java
+++ b/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionStateMachine.java
@@ -237,7 +237,7 @@ public BasicStageExecutionStats getBasicStageStats(Supplier<Iterable<TaskInfo>>
         int runningDrivers = 0;
         int completedDrivers = 0;
 
-        long cumulativeUserMemory = 0;
+        double cumulativeUserMemory = 0;
         long userMemoryReservation = 0;
         long totalMemoryReservation = 0;
 
diff --git a/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionStats.java b/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionStats.java
index 8fd01bf1e24ae..b16993807d84c 100644
--- a/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionStats.java
+++ b/presto-main/src/main/java/com/facebook/presto/execution/StageExecutionStats.java
@@ -422,7 +422,7 @@ public BasicStageExecutionStats toBasicStageStats(StageExecutionState stageExecu
                 completedDrivers,
                 rawInputDataSize,
                 rawInputPositions,
-                (long) cumulativeUserMemory,
+                cumulativeUserMemory,
                 userMemoryReservation,
                 totalMemoryReservation,
                 totalCpuTime,
diff --git a/presto-main/src/main/java/com/facebook/presto/operator/TaskContext.java b/presto-main/src/main/java/com/facebook/presto/operator/TaskContext.java
index 96663dfbb847a..3bb85e2d35e70 100644
--- a/presto-main/src/main/java/com/facebook/presto/operator/TaskContext.java
+++ b/presto-main/src/main/java/com/facebook/presto/operator/TaskContext.java
@@ -503,6 +503,9 @@ public TaskStats getTaskStats()
         updatePeakMemory();
 
         synchronized (cumulativeMemoryLock) {
+            if (lastTaskStatCallNanos == 0) {
+                lastTaskStatCallNanos = startNanos;
+            }
             double sinceLastPeriodMillis = (System.nanoTime() - lastTaskStatCallNanos) / 1_000_000.0;
             long averageMemoryForLastPeriod = (userMemory + lastUserMemoryReservation) / 2;
             cumulativeUserMemory.addAndGet(averageMemoryForLastPeriod * sinceLastPeriodMillis);
diff --git a/presto-main/src/test/java/com/facebook/presto/memory/TestMemoryTracking.java b/presto-main/src/test/java/com/facebook/presto/memory/TestMemoryTracking.java
index 24596a37dad82..92542529087a1 100644
--- a/presto-main/src/test/java/com/facebook/presto/memory/TestMemoryTracking.java
+++ b/presto-main/src/test/java/com/facebook/presto/memory/TestMemoryTracking.java
@@ -374,6 +374,22 @@ public void testDestroy()
         assertOperatorMemoryAllocations(operatorContext.getOperatorMemoryContext(), 0, 0, 0);
     }
 
+    @Test
+    public void testCumulativeUserMemoryEstimation()
+    {
+        LocalMemoryContext userMemory = operatorContext.localUserMemoryContext();
+        long userMemoryBytes = 100_000_000;
+        userMemory.setBytes(userMemoryBytes);
+        long startTime = System.nanoTime();
+        double cumulativeUserMemory = taskContext.getTaskStats().getCumulativeUserMemory();
+        long endTime = System.nanoTime();
+
+        double elapsedTimeInMillis = (endTime - startTime) / 1_000_000.0;
+        long averageMemoryForLastPeriod = userMemoryBytes / 2;
+
+        assertTrue(cumulativeUserMemory < elapsedTimeInMillis * averageMemoryForLastPeriod);
+    }
+
     private void assertStats(
             OperatorStats operatorStats,
             DriverStats driverStats,