diff --git a/src/parallel/decompositionMethods/scotchDecomp/scotchDecomp.C b/src/parallel/decompositionMethods/scotchDecomp/scotchDecomp.C
index 53931689cb..b1b666198c 100644
--- a/src/parallel/decompositionMethods/scotchDecomp/scotchDecomp.C
+++ b/src/parallel/decompositionMethods/scotchDecomp/scotchDecomp.C
@@ -253,9 +253,19 @@ Foam::label Foam::scotchDecomp::decompose
 
 
     // Check for externally provided cellweights and if so initialise weights
-    scalar maxWeights = gMax(cWeights);
+    scalar minWeights = gMin(cWeights);
     if (cWeights.size() > 0)
     {
+        if (minWeights <= 0)
+        {
+            WarningIn
+            (
+                "scotchDecomp::decompose"
+                "(const pointField&, const scalarField&)"
+            )   << "Illegal minimum weight " << minWeights
+                << endl;
+        }
+
         if (cWeights.size() != xadj.size()-1)
         {
             FatalErrorIn
@@ -266,11 +276,12 @@ Foam::label Foam::scotchDecomp::decompose
                 << " does not equal number of cells " << xadj.size()-1
                 << exit(FatalError);
         }
+
         // Convert to integers.
         velotab.setSize(cWeights.size());
         forAll(velotab, i)
         {
-            velotab[i] = int(1000000*cWeights[i]/maxWeights);
+            velotab[i] = int(cWeights[i]/minWeights);
         }
     }
 
diff --git a/src/parallel/decompositionMethods/scotchDecomp/scotchDecomp.H b/src/parallel/decompositionMethods/scotchDecomp/scotchDecomp.H
index 93bcc7b9a4..7429eefacf 100644
--- a/src/parallel/decompositionMethods/scotchDecomp/scotchDecomp.H
+++ b/src/parallel/decompositionMethods/scotchDecomp/scotchDecomp.H
@@ -104,6 +104,9 @@ public:
 
         //- Return for every coordinate the wanted processor number. Use the
         //  mesh connectivity (if needed)
+        //  Weights get truncated to convert into integer
+        //  so e.g. 3.5 is seen as 3. The overall sum of weights
+        //  might otherwise overflow.
         virtual labelList decompose
         (
             const pointField& points,
@@ -114,6 +117,7 @@ public:
         //  passed agglomeration map (from fine to coarse cells) and coarse cell
         //  location. Can be overridden by decomposers that provide this
         //  functionality natively.
+        //  See note on weights above.
         virtual labelList decompose
         (
             const labelList& agglom,
@@ -128,6 +132,7 @@ public:
         //    from 0 at processor0 and then incrementing all through the
         //    processors)
         //  - the connections are across coupled patches
+        //  See note on weights above.
         virtual labelList decompose
         (
             const labelListList& globalCellCells,
diff --git a/src/parallel/metisDecomp/metisDecomp.C b/src/parallel/metisDecomp/metisDecomp.C
index 9066e92248..fb2fddb868 100644
--- a/src/parallel/metisDecomp/metisDecomp.C
+++ b/src/parallel/metisDecomp/metisDecomp.C
@@ -89,9 +89,19 @@ Foam::label Foam::metisDecomp::decompose
 
 
     // Check for externally provided cellweights and if so initialise weights
-    scalar maxWeights = gMax(cWeights);
+    scalar minWeights = gMin(cWeights);
     if (cWeights.size() > 0)
     {
+        if (minWeights <= 0)
+        {
+            WarningIn
+            (
+                "metisDecomp::decompose"
+                "(const pointField&, const scalarField&)"
+            )   << "Illegal minimum weight " << minWeights
+                << endl;
+        }
+
         if (cWeights.size() != numCells)
         {
             FatalErrorIn
@@ -106,7 +116,7 @@ Foam::label Foam::metisDecomp::decompose
         cellWeights.setSize(cWeights.size());
         forAll(cellWeights, i)
         {
-            cellWeights[i] = int(1000000*cWeights[i]/maxWeights);
+            cellWeights[i] = int(cWeights[i]/minWeights);
         }
     }
 
diff --git a/src/parallel/metisDecomp/metisDecomp.H b/src/parallel/metisDecomp/metisDecomp.H
index c585686f60..12610f7d82 100644
--- a/src/parallel/metisDecomp/metisDecomp.H
+++ b/src/parallel/metisDecomp/metisDecomp.H
@@ -101,6 +101,9 @@ public:
 
         //- Return for every coordinate the wanted processor number. Use the
         //  mesh connectivity (if needed)
+        //  Weights get normalised so the minimum value is 1 before truncation
+        //  to an integer so the weights should be multiples of the minimum
+        //  value. The overall sum of weights might otherwise overflow.
         virtual labelList decompose
         (
             const pointField& points,
@@ -111,6 +114,7 @@ public:
         //  passed agglomeration map (from fine to coarse cells) and coarse cell
         //  location. Can be overridden by decomposers that provide this
         //  functionality natively.
+        //  See note on weights above.
         virtual labelList decompose
         (
             const labelList& agglom,
@@ -125,6 +129,7 @@ public:
         //    from 0 at processor0 and then incrementing all through the
         //    processors)
         //  - the connections are across coupled patches
+        //  See note on weights above.
         virtual labelList decompose
         (
             const labelListList& globalCellCells,
diff --git a/src/parallel/parMetisDecomp/parMetisDecomp.C b/src/parallel/parMetisDecomp/parMetisDecomp.C
index cf7434b5c9..f8e590c957 100644
--- a/src/parallel/parMetisDecomp/parMetisDecomp.C
+++ b/src/parallel/parMetisDecomp/parMetisDecomp.C
@@ -428,9 +428,19 @@ Foam::labelList Foam::parMetisDecomp::decompose
 
 
     // Check for externally provided cellweights and if so initialise weights
-    scalar maxWeights = gMax(cWeights);
+    scalar minWeights = gMin(cWeights);
     if (cWeights.size() > 0)
     {
+        if (minWeights <= 0)
+        {
+            WarningIn
+            (
+                "metisDecomp::decompose"
+                "(const pointField&, const scalarField&)"
+            )   << "Illegal minimum weight " << minWeights
+                << endl;
+        }
+
         if (cWeights.size() != mesh_.nCells())
         {
             FatalErrorIn
@@ -441,11 +451,12 @@ Foam::labelList Foam::parMetisDecomp::decompose
                 << " does not equal number of cells " << mesh_.nCells()
                 << exit(FatalError);
         }
+
         // Convert to integers.
         cellWeights.setSize(cWeights.size());
         forAll(cellWeights, i)
         {
-            cellWeights[i] = int(1000000*cWeights[i]/maxWeights);
+            cellWeights[i] = int(cWeights[i]/minWeights);
         }
     }
 
@@ -779,9 +790,19 @@ Foam::labelList Foam::parMetisDecomp::decompose
 
 
     // Check for externally provided cellweights and if so initialise weights
-    scalar maxWeights = gMax(cWeights);
+    scalar minWeights = gMin(cWeights);
     if (cWeights.size() > 0)
     {
+        if (minWeights <= 0)
+        {
+            WarningIn
+            (
+                "parMetisDecomp::decompose(const labelListList&"
+                ", const pointField&, const scalarField&)"
+            )   << "Illegal minimum weight " << minWeights
+                << endl;
+        }
+
         if (cWeights.size() != globalCellCells.size())
         {
             FatalErrorIn
@@ -792,11 +813,12 @@ Foam::labelList Foam::parMetisDecomp::decompose
                 << " does not equal number of cells " << globalCellCells.size()
                 << exit(FatalError);
         }
+
         // Convert to integers.
         cellWeights.setSize(cWeights.size());
         forAll(cellWeights, i)
         {
-            cellWeights[i] = int(1000000*cWeights[i]/maxWeights);
+            cellWeights[i] = int(cWeights[i]/minWeights);
         }
     }
 
diff --git a/src/parallel/parMetisDecomp/parMetisDecomp.H b/src/parallel/parMetisDecomp/parMetisDecomp.H
index dda8173557..69c9500a47 100644
--- a/src/parallel/parMetisDecomp/parMetisDecomp.H
+++ b/src/parallel/parMetisDecomp/parMetisDecomp.H
@@ -112,6 +112,9 @@ public:
 
         //- Return for every coordinate the wanted processor number. Use the
         //  mesh connectivity (if needed)
+        //  Weights get normalised so the minimum value is 1 before truncation
+        //  to an integer so the weights should be multiples of the minimum
+        //  value. The overall sum of weights might otherwise overflow.
         virtual labelList decompose
         (
             const pointField& points,
@@ -122,6 +125,7 @@ public:
         //  passed agglomeration map (from fine to coarse cells) and coarse cell
         //  location. Can be overridden by decomposers that provide this
         //  functionality natively.
+        //  See note on weights above.
         virtual labelList decompose
         (
             const labelList& cellToRegion,
@@ -136,6 +140,7 @@ public:
         //    from 0 at processor0 and then incrementing all through the
         //    processors)
         //  - the connections are across coupled patches
+        //  See note on weights above.
         virtual labelList decompose
         (
             const labelListList& globalCellCells,