Index: lucene/core/src/test/org/apache/lucene/util/packed/TestPackedInts.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/util/packed/TestPackedInts.java	(revision 1492085)
+++ lucene/core/src/test/org/apache/lucene/util/packed/TestPackedInts.java	(working copy)
@@ -657,6 +657,7 @@
     assertEquals(10, wrt.get(7));
     assertEquals(99, wrt.get(valueCount - 10));
     assertEquals(1 << 10, wrt.get(valueCount - 1));
+    assertEquals(RamUsageEstimator.sizeOf(wrt), wrt.ramBytesUsed());
   }
 
   public void testPagedGrowableWriter() {
@@ -684,6 +685,9 @@
       assertEquals(buf.get(i), writer.get(i));
     }
 
+    // test ramBytesUsed
+    assertEquals(RamUsageEstimator.sizeOf(writer), writer.ramBytesUsed());
+
     // test copy
     PagedGrowableWriter copy = writer.resize(_TestUtil.nextLong(random(), writer.size() / 2, writer.size() * 3 / 2));
     for (long i = 0; i < copy.size(); ++i) {
Index: lucene/core/src/java/org/apache/lucene/util/packed/PagedGrowableWriter.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/util/packed/PagedGrowableWriter.java	(revision 1492085)
+++ lucene/core/src/java/org/apache/lucene/util/packed/PagedGrowableWriter.java	(working copy)
@@ -20,6 +20,8 @@
 import static org.apache.lucene.util.packed.PackedInts.checkBlockSize;
 import static org.apache.lucene.util.packed.PackedInts.numBlocks;
 
+import org.apache.lucene.util.RamUsageEstimator;
+
 /**
  * A {@link PagedGrowableWriter}. This class slices data into fixed-size blocks
  * which have independent numbers of bits per value and grow on-demand.
@@ -128,6 +130,21 @@
     return newWriter;
   }
 
+  /** Return the number of bytes used by this object. */
+  public long ramBytesUsed() {
+    long bytesUsed = RamUsageEstimator.alignObjectSize(
+        RamUsageEstimator.NUM_BYTES_OBJECT_HEADER
+        + RamUsageEstimator.NUM_BYTES_OBJECT_REF
+        + RamUsageEstimator.NUM_BYTES_LONG
+        + 3 * RamUsageEstimator.NUM_BYTES_INT
+        + RamUsageEstimator.NUM_BYTES_FLOAT);
+    bytesUsed += RamUsageEstimator.alignObjectSize(RamUsageEstimator.NUM_BYTES_ARRAY_HEADER + (long) RamUsageEstimator.NUM_BYTES_OBJECT_REF * subWriters.length);
+    for (GrowableWriter gw : subWriters) {
+      bytesUsed += gw.ramBytesUsed();
+    }
+    return bytesUsed;
+  }
+
   @Override
   public String toString() {
     return getClass().getSimpleName() + "(size=" + size() + ",pageSize=" + pageSize() + ")";
Index: lucene/core/src/java/org/apache/lucene/util/packed/GrowableWriter.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/util/packed/GrowableWriter.java	(revision 1492085)
+++ lucene/core/src/java/org/apache/lucene/util/packed/GrowableWriter.java	(working copy)
@@ -20,6 +20,7 @@
 import java.io.IOException;
 
 import org.apache.lucene.store.DataOutput;
+import org.apache.lucene.util.RamUsageEstimator;
 
 /**     
  * Implements {@link PackedInts.Mutable}, but grows the
@@ -123,7 +124,12 @@
 
   @Override
   public long ramBytesUsed() {
-    return current.ramBytesUsed();
+    return RamUsageEstimator.alignObjectSize(
+        RamUsageEstimator.NUM_BYTES_OBJECT_HEADER
+        + RamUsageEstimator.NUM_BYTES_OBJECT_REF
+        + RamUsageEstimator.NUM_BYTES_LONG
+        + RamUsageEstimator.NUM_BYTES_FLOAT)
+        + current.ramBytesUsed();
   }
 
   @Override