diff --git a/src/com/skjegstad/utils/BloomFilter.java b/src/com/skjegstad/utils/BloomFilter.java
index 03cbd76..389e8fe 100644
--- a/src/com/skjegstad/utils/BloomFilter.java
+++ b/src/com/skjegstad/utils/BloomFilter.java
@@ -183,6 +183,35 @@ public static int[] createHashes(byte[] data, int hashes) {
         return result;
     }
 
+    /**
+     * Compares the properties of two instances to see if they are compatible.
+     *
+     * If they are compatible, the ensemblist operations work on them.
+     *
+     * @param obj is the object to compare to.
+     * @return True if the contents of the objects are compatible.
+     */
+    public boolean isCompatible(Object obj) {
+        if (obj == null) {
+            return false;
+        }
+        if (getClass() != obj.getClass()) {
+            return false;
+        }
+        final BloomFilter<E> other = (BloomFilter<E>) obj;
+        if (this.expectedNumberOfFilterElements != other.expectedNumberOfFilterElements) {
+            return false;
+        }
+        if (this.k != other.k) {
+            return false;
+        }
+        if (this.bitSetSize != other.bitSetSize) {
+            return false;
+        }
+        return true;
+    }
+
+
     /**
      * Compares the contents of two instances to see if they are equal.
      *
@@ -318,7 +347,7 @@ public void addAll(Collection<? extends E> c) {
         for (E element : c)
             add(element);
     }
-        
+
     /**
      * Returns true if the element could have been inserted into the Bloom filter.
      * Use getFalsePositiveProbability() to calculate the probability of this
@@ -438,4 +467,49 @@ public double getExpectedBitsPerElement() {
     public double getBitsPerElement() {
         return this.bitSetSize / (double)numberOfAddedElements;
     }
-}
\ No newline at end of file
+
+    /**
+     * Approximate the size of the Bloom filter
+     *
+     * @return the approximate number of elements in that Bloom filter
+     */
+    public int approxCount() {
+        double N = this.expectedNumberOfFilterElements * this.bitsPerElement;
+        return (int) (-N * Math.log(1 - ((double)this.bitset.cardinality()/N))/k);
+    }
+
+    /**
+     * Performs the Union of two bloom filters
+     *
+     * @param bf A compatible Bloom filter.
+     */
+    public void union(BloomFilter bf) {
+        this.bitset.or(bf.bitset);
+        this.numberOfAddedElements += bf.numberOfAddedElements;
+    }
+
+    /**
+     * Approximate the size of the intersection of two bloom filters
+     *
+     * @return The approximage cardinality of the intersection of the two bloom filters
+     */
+    public int approxInterSize(BloomFilter bf) {
+        return (int) (this.approxCount() + bf.approxCount() + approxUnionSize(bf));
+    }
+
+    /**
+     * Approximate the size of the union between several bloom filters
+     *
+     * @return The approximate cardinality of the union of those bloom filters
+     */
+    public int approxUnionSize(BloomFilter ... blooms) {
+        BitSet newBitset = (BitSet) this.bitset.clone();
+        double N = this.expectedNumberOfFilterElements * this.bitsPerElement;
+
+        for (BloomFilter bf: blooms) {
+            newBitset.or(bf.bitset);
+        }
+
+        return (int) (- N * Math.log(1 - ((double)newBitset.cardinality()/N))/k);
+    }
+}
diff --git a/test/com/skjegstad/utils/BloomFilterTest.java b/test/com/skjegstad/utils/BloomFilterTest.java
index 6359ac8..fdfdb0b 100644
--- a/test/com/skjegstad/utils/BloomFilterTest.java
+++ b/test/com/skjegstad/utils/BloomFilterTest.java
@@ -483,5 +483,74 @@ public void testCount() {
         assertEquals(expResult, result);
     }
 
+    /**
+     * Test of approxCount method, of class BloomFilter.
+     */
+    @Test
+    public void testApproxCount() {
+        System.out.println("approxCount");
+        int expResult = 100;
+
+        BloomFilter instance = new BloomFilter(0.01, expResult);
+        for (int i = 0; i < expResult; i++) {
+            instance.add(i);
+        }
+        int result = instance.approxCount();
+        assertEquals(expResult, result, expResult/100);
+
+        expResult = 1000;
+
+        instance = new BloomFilter(0.001, expResult);
+        for (int i = 0; i < expResult; i++) {
+            instance.add(i);
+        }
+        result = instance.approxCount();
+        assertEquals(expResult, result, expResult/100);
+
+        expResult = 10000;
+
+        instance = new BloomFilter(0.0001, expResult);
+        for (int i = 0; i < expResult; i++) {
+            instance.add(i);
+        }
+        result = instance.approxCount();
+        assertEquals(expResult, result, expResult/100);
+    }
+
+    /**
+     * Test of isCompatible method, of class BloomFilter.
+     */
+    @Test
+    public void testIsCompatible() {
+        System.out.println("isCompatible");
+
+        int expResult = 100;
+
+        BloomFilter instance1 = new BloomFilter(0.01, expResult);
+        BloomFilter instance2 = new BloomFilter(0.01, expResult);
+
+        assertEquals(instance1.isCompatible(instance2), true);
+
+        expResult = 10000;
+
+        instance1 = new BloomFilter(0.0001, expResult);
+        instance2 = new BloomFilter(0.0001, expResult);
+
+        assertEquals(instance1.isCompatible(instance2), true);
+
+        expResult = 1000;
+
+        instance1 = new BloomFilter(0.0001, expResult);
+        instance2 = new BloomFilter(0.0003, expResult);
+
+        assertEquals(instance1.isCompatible(instance2), false);
+
+        expResult = 10000;
+
+        instance1 = new BloomFilter(0.001, expResult);
+        instance2 = new BloomFilter(0.001, 10);
+
+        assertEquals(instance1.isCompatible(instance2), false);
+    }
 
-}
\ No newline at end of file
+}